Sample records for energy vibrational structure

The present thesis deals with fundamental researches on passive and active vibration control of renewable energystructures, and provides useful models for practical applications. Effective and robust vibration control methods have been explored for mitigating the lightly damped edgewise blade...... solutions for wave energy point absorbers, in order to maximize the mean absorbed power and to deliver more smooth power to the grid. A novel suboptimal causal control law has been established for controlling the motion of the point absorber, and a new type of point absorber has also been proposed...

to the long-term structural health of a building or bridge, but at the same time they can be exploited as a power source to power the wireless sensors that are monitoring this structural health. This paper presents a new energy harvesting method based on a vibration driven electromagnetic harvester. By using......The use of wireless sensors for structural health monitoring offers several advantages such as small size, easy installation and minimal intervention on existing structures. However the most significant concern about such wireless sensors is the lifetime of the system, which depends heavily...... on the type of power supply. No matter how energy efficient the operation of a battery operated sensor is, the energy of the battery will be exhausted at some point. In order to achieve a virtually unlimited lifetime, the sensor node should be able to recharge its battery in an easy way. Energy harvesting...

A dimension-wise method for predicting fuzzy energy flows between structuralvibrating systems coupled by joints with epistemic uncertainties is established. Based on its Legendre polynomial approximation at α=0, both the minimum and maximum point vectors of the energy flow of interest are calculated dimension by dimension within the space spanned by the interval parameters determined by fuzzy those at α=0 and the resulted interval bounds are used to assemble the concerned fuzzy energy flows. Besides the proposed method, vertex method as well as two current methods is also applied. Comparisons among results by different methods are accomplished by two numerical examples and the accuracy of all methods is simultaneously verified by Monte Carlo simulation.

Full Text Available In this paper, we investigate the control of 2D flexible structures by vibration confinement and the regulation of their energy flow along prespecified spatial paths. A discretized-model-based feedback strategy, aiming at confining and suppressing simultaneously the vibration, is proposed. It is assumed that the structure consists of parts that are sensitive to vibrations. The control design introduces a new pseudo-modal matrix derived from the computed eigenvectors of the discretized model. Simulations are presented to show the efficacy of the proposed control law. A parametric study is carried out to examine the effects of the different control parameters on the simultaneous confinement and suppression of vibrations. In addition, we conducted a set of simulations to investigate the flow control of vibrationalenergy during the confinement-suppression process. We found that the energy flow can be regulated via a set of control parameters for different confinement configurations.

The feasibility of a vibration based damage identification method is investigated. The Modal Strain Energy method is applied to a T–beam structure. The dynamic response of an intact structure and a damaged, delaminated structure is analysed employing a commercially available Finite Element package.

Full Text Available We introduce a design with dual resonant structure which can harvest energy from random vibration sources at low frequency range. The dual resonant structure consists of two spring-mass subsystems with different frequency responses, which exhibit strong coupling and broad bandwidth when the two masses collide with each other. Experiments with piezoelectric elements show that the energy harvesting device with dual resonant structure can generate higher power output than the sum of the two separate devices from random vibration sources.

In this paper, we present design and test of a broadband electrostatic energy harvester with a dual resonant structure, which consists of two cantilever-mass subsystems each with a mass attached at the free edge of a cantilever. Comparing to traditional devices with single resonant frequency, the proposed device with dual resonant structure can resonate at two frequencies. Furthermore, when one of the cantilever-masses is oscillating at resonance, the vibration amplitude is large enough to make it collide with the other mass, which provides strong mechanical coupling between the two subsystems. Therefore, this device can harvest a decent power output from vibration sources at a broad frequency range. During the measurement, continuous power output up to 6.2-9.8 μW can be achieved under external vibration amplitude of 9.3 m/s 2 at a frequency range from 36.3 Hz to 48.3 Hz, which means the bandwidth of the device is about 30% of the central frequency. The broad bandwidth of the device provides a promising application for energy harvesting from the scenarios with random vibration sources. The experimental results indicate that with the dual resonant structure, the vibration-to-electricity energy conversion efficiency can be improved by 97% when an external random vibration with a low frequency filter is applied.

Full Text Available As an important parameter in blasting design, charging structure directly influences blasting effect. Due to complex conditions of this blasting and excavating engineering in Jiangsu, China, the authors carried out comparative researches with coupling structure, air-decoupling structure, and water-decoupling structure. After collecting, comparing, and analyzing produced signals on blasting vibration, the authors summarized that when proportional distances are the same, water-decoupling structure can reduce instantaneous energy of blasting vibration more effectively with more average rock fragmentation and less harm of dust. From the perspective of impedance matching, the present paper analyzed influence of charging structure on blasting vibrationenergy, demonstrating that impedance matching relationship between explosive and rock changes because of different charging structures. Through deducing relationship equation that meets the impedance matching of explosive and rock under different charging structures, the research concludes that when blasting rocks with high impedance, explosive with high impedance can better transmits blasting energy. Besides, when employing decoupling charging, there exists a reasonable decoupling coefficient helping realize impedance matching of explosive and rock.

Combining Goldenveizer-Novozhilov shell theory, thin plate theory and electro-elastic surface theory, the size-dependent vibration of nano-sized piezoelectric double-shell structures under simply supported boundary condition is presented, and the surface energy effect on the natural frequencies is discussed. The displacement components of the cylindrical nano-shells and annular nano-plates are expanded as the superposition of standard Fourier series based on Hamilton's principle. The total stresses with consideration of surface energy effect are derived, and the total energy function is obtained by using Rayleigh-Ritz energy method. The free vibration equation is solved, and the natural frequency is analyzed. In numerical examples, it is found that the surface elastic constant, piezoelectric constant and surface residual stress show different effects on the natural frequencies. The effect of surface piezoelectric constant is the maximum. The effect of dimensions of the double-shell under different surface material properties is also examined.

By scavenging energy from their local environment, portable electronic devices such as MEMS devices, mobile phones, radios and wireless sensors can achieve greater run times with potentially lower weight. Vibrationenergy harvesting is one such approach where energy from parasitic vibrations can be converted into electrical energy through the use of piezoelectric and electromagnetic transducers. Parasitic vibrations come from a range of sources such as human movement, wind, seismic forces and traffic. Existing approaches to vibrationenergy harvesting typically utilize a rectifier circuit, which is tuned to the resonant frequency of the harvesting structure and the dominant frequency of vibration. We have developed a novel approach to vibrationenergy harvesting, including adaptation to non-periodic vibrations so as to extract the maximum amount of vibrationenergy available. Experimental results of an experimental apparatus using an off-the-shelf transducer (i.e. speaker coil) show mechanical vibration to electrical energy conversion efficiencies of 27–34%

and experiments with piezoelectric elements show that the energy harvesting device with the bi-resonant structure can generate higher power output than that of the sum of the two separate devices from random vibration sources at low frequency, and hence significantly improves the vibration-to- electricity......This paper reports on a bi-resonant structure of piezoelectric PVDF films energy harvester (PPEH), which consists of two cantilevers with resonant frequencies of 15 Hz and 22 Hz. With increased acceleration, the vibration amplitudes of the two cantilever-mass structures are increased and collision...

Full Text Available Abstract Structural Health Monitoring (SHM of Tension Leg Platform (TLP is very crucial for preventing catastrophic and sudden collapse of the structures. One of the methods of monitoring these structures is implementing SHM sensors. Supplying energy for these sensors for a long period is a challenging problem. So, one of the new methods of supplying energy for SHM, is usage of mechanical energy. In this method, the piezoelectric material is employed to convert the mechanical energy which is resulted from vibration of structure, to electrical energy. The advantage of this method is based on not implementing the battery charging system. Therefore, in this paper, after modeling TLP structure, energy supplying of these sensors with piezoelectric converters is studied. Furthermore, fault diagnosis of these structures in the presence of different uncertainties is proposed by the features of voltage signal, produced from piezoelectric patches and fuzzy classification method. Results show that this method can diagnose faults of the structure with an acceptable success rate.

Full Text Available Using Vibro-Impact Nonlinear Energy Sinks (VI NESs is one of the novel strategies to control structuralvibrations and mitigate their seismic response. In this system, a mass is tuned on the structure floor, so that it has a specific distance from an inelastic constraint connected to the floor mass. In case of structure stimulation, the displaced VI NES mass collides with the inelastic constraint and upon impacts, energy is dissipated. In the present work, VI NES is studied when its parameters, including clearance and stiffness ratio, are simultaneously optimized. Harmony search as a recent meta-heuristic algorithm is efficiently specialized and utilized for the aforementioned continuous optimization problem. The optimized attached VI NES is thus shown to be capable of interacting with the primary structure over a wide range of frequencies. The resulting controlled response is then investigated, in a variety of low and medium rise steel moment frames, via nonlinear dynamic time history analyses. Capability of the VI NES to dissipate siesmic input energy of earthquakes and their capabilitiy in reducing response of srtructures effectively, through vibro-impacts between the energy sink’s mass and the floor mass, is discussed by extracting several performance indices and the corresponding Fourier spectra. Results of the numerical simulations done on some structural model examples reveal that the optimized VI NES has caused successive redistribution of energy from low-frequency high-amplitude vibration modes to high-frequency low-amplitude modes, bringing about the desired attenuation of the structural responses.

Full Text Available As an alternative to traditional cantilever beam structures and their evolutions, a flexible beam based, interdigital structure, vibrationenergy harvester has been presented and investigated. The proposed interdigital-shaped oscillator consists of a rectangular flexible frame and series of cantilever beams interdigitally bonded to it. In order to achieve low frequency and wide-bandwidth harvesting, Young’s modulus of materials, frame size and the amount of the cantilevers have been studied systematically. The measured frequency responses of the designed device (PDMS frame, quintuple piezoelectric cantilever beams show a 460% increase in bandwidth below 80Hz. When excited at an acceleration of 1.0 g, the energy harvester achieves to a maximum open-circuit voltage of 65V, and the maximum output power 4.5 mW.

Li, Pengwei, E-mail: lipengwei@tyut.edu.cn; Wang, Yanfen; Luo, Cuixian; Li, Gang; Hu, Jie; Zhang, Wendong [MicroNano System Research Center of College of Information Engineering and Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Liu, Ying [MicroNano System Research Center of College of Information Engineering and Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Baicheng Ordnance Test Center of China, Baicheng 137000, Jilin (China); Liu, Wei [Baicheng Ordnance Test Center of China, Baicheng 137000, Jilin (China)

2015-04-15

As an alternative to traditional cantilever beam structures and their evolutions, a flexible beam based, interdigital structure, vibrationenergy harvester has been presented and investigated. The proposed interdigital-shaped oscillator consists of a rectangular flexible frame and series of cantilever beams interdigitally bonded to it. In order to achieve low frequency and wide-bandwidth harvesting, Young’s modulus of materials, frame size and the amount of the cantilevers have been studied systematically. The measured frequency responses of the designed device (PDMS frame, quintuple piezoelectric cantilever beams) show a 460% increase in bandwidth below 80Hz. When excited at an acceleration of 1.0 g, the energy harvester achieves to a maximum open-circuit voltage of 65V, and the maximum output power 4.5 mW.

Mode shapes in the design of mechanical energy harvesters, as a means of performance increase, have been largely overlooked. Currently, the vast majority of energy harvester designs employ some variation of a single-degree-of-freedom cantilever, and the mode shapes of such beams are well known. This is especially true for the first bending mode, which is almost exclusively the chosen vibration mode for energy harvesting. Two-dimensional beam shapes (those which curve, meander, spiral, etc., in a plane) have recently gained research interest, as they offer freedom to modify the vibration characteristics of the harvester beam for achieving higher power density. In this study, the second bending mode shape of the “Elephant” two-dimensional beam shape is examined, and its interaction with the first bending mode is evaluated. A combinatory mode shape created by using mass loading structural modification to lower the second bending modal frequency was found to interact with the first bending mode. This is possible since the first two bending modes do not share common areas of displacement. The combined mode shape is shown to produce the most power of any of the considered mode shapes.

Conversion of ambient vibrationalenergy into electric power has been the impetus of much modern research. The traditional analysis has focused on absolute electrical power output from the harvesting devices and efficiency defined as the convertibility of an infinite resource of vibration excitation into power. This perspective has limited extensibility when applying resonant harvesters to host resonant structures when the inertial influence of the harvester is more significant. Instead, this work pursues a fundamental understanding of the coupled dynamics of a main mass-spring-damper system to which an electromagnetic or piezoelectric mass-spring-damper is attached. The governing equations are derived, a metric of efficiency is presented, and analysis is undertaken. It is found that electromagnetic energy harvesting efficiency and maximum power output is limited by the strength of the coupling such that no split system resonances are induced for a given mass ratio. For piezoelectric harvesters, only the coupling strength and certain design requirements dictate maximum power and efficiency achievable. Since the harvesting circuitry must "follow" the split resonances as the piezoelectric harvesters become more massive, the optimum design of piezoelectric harvesters appears to be more involved than for electromagnetic devices.

The Energy Finite Element Analysis (EFEA) has been utilized successfully for modeling complex structural-acoustic systems with isotropic structural material properties. In this paper, a formulation for modeling structures made out of composite materials is presented. An approach based on spectral finite element analysis is utilized first for developing the equivalent material properties for the composite material. These equivalent properties are employed in the EFEA governing differential equations for representing the composite materials and deriving the element level matrices. The power transmission characteristics at connections between members made out of non-isotropic composite material are considered for deriving suitable power transmission coefficients at junctions of interconnected members. These coefficients are utilized for computing the joint matrix that is needed to assemble the global system of EFEA equations. The global system of EFEA equations is solved numerically and the vibration levels within the entire system can be computed. The new EFEA formulation for modeling composite laminate structures is validated through comparison to test data collected from a representative composite aircraft fuselage that is made out of a composite outer shell and composite frames and stiffeners. NASA Langley constructed the composite cylinder and conducted the test measurements utilized in this work.

This paper reports the design and test of a miniature coupled bistable vibrationenergy harvester. Operation of a bistable structure largely depends on vibration amplitude rather than frequency, which makes it very promising for wideband vibrationenergy harvesting applications. A coupled bistable structure consists of a pair of mobile magnets that create two potential wells and thus the bistable phenomenon. It requires lower excitation to trigger bistable operation compared to conventional bistable structures. Based on previous research, this work focused on miniaturisation of the coupled bistable structure for energy harvesting application. The proposed bistable energy harvester is a combination of a Duffing's nonlinear structure and a linear assisting resonator. Experimental results show that the output spectrum of the miniature coupled bistable vibrationenergy harvester was the superposition of several spectra. It had a higher maximum output power and a much greater bandwidth compared to simply the Duffing's structure without the assisting resonator

The field of energy harvesting has grown concurrently with the rapid development of portable and wireless electronics in which reliable and long-lasting power sources are required. Electrochemical batteries have a limited lifespan and require periodic recharging. In contrast, vibrationenergy harvesters can supply uninterrupted power by scavenging useful electrical energy from ambient structuralvibrations. This article reviews the current state of vibrationenergy harvesters based on magnetostrictive materials, especially Terfenol-D and Galfenol. Existing magnetostrictive harvester designs are compared in terms of various performance metrics. Advanced techniques that can reduce device size and improve performance are presented. Models for magnetostrictive devices are summarized to guide future harvester designs.

Modal coupling is an important issue in the analysis and control of structural systems with multi-degrees of freedom (MDOF). In this paper, modal coupling induced by energy conversion in the structural control of an MDOF system using a synchronized switch damping method is investigated theoretically and validated numerically. In the analysis, it is supposed that the voltage on the piezoelectric actuator is switched at the displacement extrema of a given mode. Two types of coupling in energy conversion are considered. The first is whether the switching action based on one mode induces energy conversion of the other modes. The second is whether the vibration of one mode affects the energy conversion of the other modes. The results indicate that the modal coupling in energy conversion is very complicated. In most cases the switching action based on one mode does induce energy conversion of another mode, but the efficiency depends on the frequency ratio of the two modes. The vibration of one mode affects the energy conversion of another mode only when the frequency ratio of the two modes takes some special values. Discussions are also given on the potential application of the theoretical results in the design of an energy harvesting device. (paper)

Interaction energies, molecular structure and vibrational frequencies of the binary complex formed between H(D)Cl and dimethyl ether have been obtained using quantum-chemical methods. Equilibrium and vibrationally averaged structures, harmonic and anharmonic wavenumbers of the complex and its deuterated isotopomer were calculated using harmonic and anharmonic second-order perturbation theory procedures with Density Functional Theory B3LYP and B2PLYP-D and ab initio Møller-Plesset second-order methods, and a 6-311++G(3d,3p) basis set. A phenomenological model describing anharmonic-type vibrational couplings within hydrogen bonds was developed to explain the unique broadening and fine structure, as well as the isotope effect of the Cl–H and Cl–D stretching IR absorption bands in the gaseous complexes with dimethyl ether, as an effect of hydrogen bond formation. Simulations of the rovibrational structure of the Cl–H and Cl–D stretching bands were performed and the results were compared with experimental spectra.

VibrationEnergy Harvesting is an emerging technology aimed at turning mechanical energy from vibrations into electricity to power microsystems of the future. Most of present vibrationenergy harvesters are based on a mass spring structure introducing a resonance phenomenon that allows to increase the output power compared to non-resonant systems, but limits the working frequency bandwidth. Therefore, they are not able to harvest energy when ambient vibrations' frequencies shift. To follow sh...

Full Text Available For health monitoring of bridges, wireless acceleration sensor nodes (WASNs are normally used. In bridge environment, several forms of energy are available for operating WASNs that include wind, solar, acoustic, and vibrationenergy. However, only bridge vibration has the tendency to be utilized for embedded WASNs application in bridge structures. This paper reports on the recent advancements in the area of vibrationenergy harvesters (VEHs utilizing bridge oscillations. The bridge vibration is narrowband (1 to 40 Hz with low acceleration levels (0.01 to 3.8 g. For utilization of bridge vibration, electromagnetic based vibrationenergy harvesters (EM-VEHs and piezoelectric based vibrationenergy harvesters (PE-VEHs have been developed. The power generation of the reported EM-VEHs is in the range from 0.7 to 1450000 μW. However, the power production by the developed PE-VEHs ranges from 0.6 to 7700 μW. The overall size of most of the bridge VEHs is quite comparable and is in mesoscale. The resonant frequencies of EM-VEHs are on the lower side (0.13 to 27 Hz in comparison to PE-VEHs (1 to 120 Hz. The power densities reported for these bridge VEHs range from 0.01 to 9539.5 μW/cm3 and are quite enough to operate most of the commercial WASNs.

Full Text Available Lightweight pre-cast flooring systems using post-tensioning to increase strength but not stiffness are increasingly popular, and vibration serviceability problems tend to govern design of such floors where human occupants are increasingly concerned with vibrations. At the same time as inducing response, stationary human observers can also participate in the response as mitigating influence and it is clear that a human behaves as a highly effective damper, even when seated.

Full Text Available The vibrationenergy harvesting process represents one of the research directions for increasing power efficiency of electric systems, increasing instrumentation nodes autonomy in hard to reach locations and decreasing total system mass by eliminating cables and higher-power adapters. Research based on the possibility of converting vibrationenergy into useful electric energy is used to evaluate the potential of its use on turbomachinery applications. Aspects such as the structure and characteristics of piezoelectric generators, harvesting networks, their setup and optimization, are considered. Finally, performance test results are shown using piezoelectric systems on a turbine engine.

This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author at the Uni...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....

The goal of this project is to develop an efficient energy scavenger for converting ambient low-frequency vibrations into electrical power. In order to achieve this a novel inertial micro power generator architecture has been developed that utilizes the bi-stable motion of a mechanical mass to convert a broad range of low-frequency (< 30Hz), and large-deflection (>250 {micro}m) ambient vibrations into high-frequency electrical output energy. The generator incorporates a bi-stable mechanical structure to initiate high-frequency mechanical oscillations in an electromagnetic scavenger. This frequency up-conversion technique enhances the electromechanical coupling and increases the generated power. This architecture is called the Parametric Frequency Increased Generator (PFIG). Three generations of the device have been fabricated. It was first demonstrated using a larger bench-top prototype that had a functional volume of 3.7cm3. It generated a peak power of 558{micro}W and an average power of 39.5{micro}W at an input acceleration of 1g applied at 10 Hz. The performance of this device has still not been matched by any other reported work. It yielded the best power density and efficiency for any scavenger operating from low-frequency (<10Hz) vibrations. A second-generation device was then fabricated. It generated a peak power of 288{micro}W and an average power of 5.8{micro}W from an input acceleration of 9.8m/s{sup 2} at 10Hz. The device operates over a frequency range of 20Hz. The internal volume of the generator is 2.1cm{sup 3} (3.7cm{sup 3} including casing), half of a standard AA battery. Lastly, a piezoelectric version of the PFIG is currently being developed. This device clearly demonstrates one of the key features of the PFIG architecture, namely that it is suitable for MEMS integration, more so than resonant generators, by incorporating a brittle bulk piezoelectric ceramic. This is the first micro-scale piezoelectric generator capable of <10Hz operation. The

A novel dynamic vibration absorber (DVA) configuration is introduced for simultaneous vibration suppression and energy harvesting from oscillations typically exhibited by large-scale low-frequency engineering structures and structural components. The proposed configuration, termed energy harvesting-enabled tuned mass-damper-inerter (EH-TMDI) comprises a mass grounded via an in-series electromagnetic motor (energy harvester)-inerter layout, and attached to the primary structure through linear spring and damper in parallel connection. The governing equations of motion are derived and solved in the frequency domain, for the case of harmonically-excited primary structures, here modelled as damped single-degree- of-freedom (SDOF) systems. Comprehensive parametric analyses proved that by varying the mass amplification property of the grounded inerter, and by adjusting the stiffness and the damping coefficients using simple optimum tuning formulae, enhanced vibration suppression (in terms of primary structure peak displacement) and energy harvesting (in terms of relative velocity at the terminals of the energy harvester) may be achieved concurrently and at nearresonance frequencies, for a fixed attached mass. Hence, the proposed EH-TMDI allows for relaxing the trade-off between vibration control and energy harvesting purposes, and renders a dual-objective optimisation a practically-feasible, reliable task. (paper)

We present an efficient approach for generating highly accurate molecular potential energy surfaces (PESs) using self-correcting, kernel ridge regression (KRR) based machine learning (ML). We introduce structure-based sampling to automatically assign nuclear configurations from a pre-defined grid to the training and prediction sets, respectively. Accurate high-level ab initio energies are required only for the points in the training set, while the energies for the remaining points are provided by the ML model with negligible computational cost. The proposed sampling procedure is shown to be superior to random sampling and also eliminates the need for training several ML models. Self-correcting machine learning has been implemented such that each additional layer corrects errors from the previous layer. The performance of our approach is demonstrated in a case study on a published high-level ab initio PES of methyl chloride with 44 819 points. The ML model is trained on sets of different sizes and then used to predict the energies for tens of thousands of nuclear configurations within seconds. The resulting datasets are utilized in variational calculations of the vibrationalenergy levels of CH3Cl. By using both structure-based sampling and self-correction, the size of the training set can be kept small (e.g., 10% of the points) without any significant loss of accuracy. In ab initio rovibrational spectroscopy, it is thus possible to reduce the number of computationally costly electronic structure calculations through structure-based sampling and self-correcting KRR-based machine learning by up to 90%.

at the University of Southern Denmark, it reports on fundamental formulas and makes uses of graphical representation to promote understanding. Thanks to the emphasis put on analytical methods and numerical results, the book is meant to make students and engineers familiar with all fundamental equations...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....

Vibrational fingerprints of small PtnP2n (n = 1–5) clusters were computed from their low-lying structures located from a global exploration of their DFT potential energy surfaces with the GSAM code. Five DFT methods were assessed from the CCSD(T) wavenumbers of PtP2 species and CCSD relative energies of Pt2P4 structures. The eight first PtnP2n isomers found are reported. The vibrational computations reveal (i) the absence of clear signatures made by overtone or combination bands due to very weak mechanical and electrical anharmonicities and (ii) some significant and recurrent vibrational fingerprints in correlation with the different PP bonding situations in the PtnP2n structures.

Vibrational fingerprints of small PtnP2n (n = 1–5) clusters were computed from their low-lying structures located from a global exploration of their DFT potential energy surfaces with the GSAM code. Five DFT methods were assessed from the CCSD(T) wavenumbers of PtP2 species and CCSD relative energies of Pt2P4 structures. The eight first PtnP2n isomers found are reported. The vibrational computations reveal (i) the absence of clear signatures made by overtone or combination bands due to very weak mechanical and electrical anharmonicities and (ii) some significant and recurrent vibrational fingerprints in correlation with the different PP bonding situations in the PtnP2n structures.

This work presents a small-scale wideband piezomagnetoelastic vibrationenergy harvester (VEH) aimed for operation at frequencies of a few hundred Hz. The VEH consists of a tape-casted PZT cantilever with thin sheets of iron foil attached on each side of the free tip. The wideband operation...... is achieved by placing the cantilever in a magnetic field induced by either one or two magnets located oppositely of the cantilever. The attraction force created by the magnetic field and iron foils introduces a mechanical force in opposite direction of the cantilevers restoring force causing a spring...

A piezoelectric vibrationenergy harvester (PVEH) is capable of converting waste or undesirable ambient vibrationenergy into useful electric energy. However, conventional PVEHs typically work in a narrow frequency range, leading to low efficiency in practical application. This work proposes a PVEH based on the principle of the nonlinear energy sink (NES) to achieve broadband energy harvesting. An alternating current circuit with a resistive load is first considered in the analysis of the dynamic properties and electric performance of the NES-based PEVH. Then, a standard rectifying direct current (DC) interface circuit is developed to evaluate the DC power from the PVEH. To gain insight into the NES mechanism involved, approximate analysis of the proposed PVEH systems under harmonic excitation is sought using the mixed multi-scale and harmonic balance method and the Newton–Raphson harmonic balance method. In addition, an equivalent circuit model (ECM) of the electromechanical system is derived and circuit simulations are conducted to explore and validate the energy harvesting and vibration absorption performance of the proposed NES-based PVEH. The response is also compared with that obtained by direct numerical integration of the equations of motion. Finally, the optimal resistance to obtain the maximum DC power is determined based on the Newton–Raphson harmonic balance method and validated by the ECM. In general, the NES-based PVEH can absorb the vibration from the primary structure and collect electric energy within a broad frequency range effectively.

In this study, fundamental issues related to bandwidth and nonlinear resonance in vibrationalenergy harvesting devices are investigated. The results show that using bandwidth as a criterion to measure device performance can be misleading. For a linear device, an enlarged bandwidth is achieved at the cost of sacrificing device performance near resonance, and thus widening the bandwidth may offer benefits only when the natural frequency of the linear device cannot match the dominant excitation frequency. For a nonlinear device, since the principle of superposition does not apply, the ''broadband" performance improvements achieved for single-frequency excitations may not be achievable for multi-frequency excitations. It is also shown that a large-amplitude response based on the traditional ''nonlinear resonance" does not always result in the optimal performance for a nonlinear device because of the negative work done by the excitation, which indicates energy is returned back to the excitation. Such undesired negative work is eliminated at global resonance, a generalized resonant condition for both linear and nonlinear systems. While the linear resonance is a special case of global resonance for a single-frequency excitation, the maximum potential of nonlinear energy harvesting can be reached for multi-frequency excitations by using global resonance to simultaneously harvest energy distributed over multiple frequencies.

This paper studies the feasibility of vibrationenergy harvesting using a Halbach array. A Halbach array is a specific arrangement of permanent magnets that concentrates the magnetic field on one side of the array while cancelling the field to almost zero on the other side. This arrangement can improve electromagnetic coupling in a limited space. The Halbach array offers an advantage over conventional layouts of magnets in terms of its concentrated magnetic field and low-profile structure, which helps improve the output power of electromagnetic energy harvesters while minimizing their size. Another benefit of the Halbach array is that due to the existence of an almost-zero magnetic field zone, electronic components can be placed close to the energy harvester without any chance of interference, which can potentially reduce the overall size of a self-powered device. The first reported example of a low-profile, planar electromagnetic vibrationenergy harvester utilizing a Halbach array was built and tested. Results were compared to ones for energy harvesters with conventional magnet layouts. By comparison, it is concluded that although energy harvesters with a Halbach array can have higher magnetic field density, a higher output power requires careful design in order to achieve the maximum magnetic flux gradient. (paper)

Full Text Available This paper reports on the design and evaluation of vibration-based piezoelectric energy-harvesting devices based on a polyvinylidene fluoride unimorph cantilever beam attached to the front of a dynamic magnifier. Experimental studies of the electromechanical frequency response functions are studied for the first three resonance frequencies. An analytical analysis is undertaken by applying the chain matrix in order to predict output voltage and output power with respect to the vibration frequency. The proposed harvester was modeled using MATLAB software and COMSOL multi- physics to study the mode shapes and electrical output parameters. The voltage and power output of the energy harvester with a dynamic magnifier was 2.62 V and 13.68 mW, respectively at the resonance frequency of the second mode. The modeling approach provides a basis to design energy harvesters exploiting dynamic magnification for improved performance and bandwidth. The potential application of such energy harvesting devices in the transport sector include autonomous structural health monitoring systems that often include embedded sensors, data acquisition, wireless communication, and energy harvesting systems.

Full Text Available The data presented in this article is in relation to the research article “Vibrationenergy harvesting based monitoring of an operational bridge undergoing forced vibration and train passage” Cahill et al. (2018 [1]. The article provides data on the full-scale bridge testing using piezoelectric vibrationenergy harvesters on Pershagen Bridge, Sweden. The bridge is actively excited via a swept sinusoidal input. During the testing, the bridge remains operational and train passages continue. The test recordings include the voltage responses obtained from the vibrationenergy harvesters during these tests and train passages. The original dataset is made available to encourage the use of energy harvesting for Structural Health Monitoring.

An adaptive diagnostic procedure for vibratingstructures based on correspondence between current estimates of stiffness matrix and structure status is proposed. Procedure employs adaptive mathematical description of the vibratingstructure in frequency domain, statistical techniques for detection and location of changes of structure properties, 'recognition' and prediction of defects. (orig.)

Full Text Available Safe localization of trains via GPS and wireless sensors is essential for railway traffic supervision. Especially for freight trains and because normally no power source is available on the wagons, special solutions for energy supply have to be developed based on energy harvesting techniques. Since vibration is available in this case, it provides an interesting source of energy. Nevertheless, in order to have an efficient design of the harvesting system, the existing vibration needs to be investigated. In this paper, we focus on the characterization of vibration parameters in railway application. We propose an electromagnetic vibration converter especially developed to this application. Vibration profiles from a train traveling between two German cities were measured using a data acquisition system installed on the train’s wagon. Results show that the measured profiles present multiple frequency signals in the range of 10 to 50 Hz and an acceleration of up to 2 g. A prototype for a vibration converter is designed taking into account the real vibration parameters, robustness and integrability requirements. It is based on a moving coil attached to a mechanical spring. For the experimental emulation of the train vibrations, a shaker is used as an external artificial vibration source controlled by a laser sensor in feedback. A maximum voltage of 1.7 V peak to peak which corresponds to a maximum of 10 mW output power where the applied excitation frequency is close to the resonant frequency of the converter which corresponds to 27 Hz.

Vibrational and rotational energy relaxation in liquids are studied by means of computer simulations. As a precursor for studying vibrationalenergy relaxation of a solute molecule subsequent to the formation of a chemical bond, the validity of the classical Bersohn-Zewail model for describing......, the vibrationalenergy relaxation of I2 subsequent to photodissociation and recombination in CCl4 is studied using classical Molecular Dynamics simulations. The vibrational relaxation times and the time-dependent I-I pair distribution function are compared to new experimental results, and a qualitative agreement...... is found in both cases. Furthermore, the rotational energy relaxation of H2O in liquid water is studied via simulations and a power-and-work analysis. The mechanism of the energy transfer from the rotationally excited H2O molecule to its water neighbors is elucidated, i.e. the energy-accepting degrees...

This article describes an energy method of assessing protection effectiveness of anti-vibration gloves on the human dynamic structure. The study uses dynamic models of the human and the glove specified in Standard No. ISO 10068:2012. The physical models of human-tool systems were developed by combining human physical models with a power tool model. The combined human-tool models were then transformed into mathematical models from which energy models were finally derived. Comparative energy analysis was conducted in the domain of rms powers. The energy models of the human-tool systems were solved using numerical simulation implemented in the MATLAB/Simulink environment. The simulation procedure demonstrated the effectiveness of the anti-vibration glove as a method of protecting human operators of hand-held power tools against vibration. The desirable effect is achieved by lowering the flow of energy in the human-tool system when the anti-vibration glove is employed.

This study proposes a piezoelectric vibrationenergy harvester composed of two diagonally segmented energy harvesting units. An auxiliary structural unit is attached to the tip of a host structural unit cantilevered to a vibrating base, where the two components have beam axes in opposite directions from each other and matched short-circuit resonant frequencies. Contrary to the usual observations in two resonant frequency-matched structures, the proposed structure shows little eigenfrequency separation and yields a mode sequence change between the first two modes. These lead to maximum power generation around a specific frequency. By using commercial finite element software, it is shown that the magnitude of the output power from the proposed vibrationenergy harvester can be substantially improved in comparison with those from conventional cantilevered energy harvesters with the same footprint area and magnitude of a tip mass.

In September 2016, a gas compressor in offshore Sarawak has its rotor changed out. Prior to this change-out, pipe vibration study was carried-out by the project team to evaluate any potential high energy pipe vibration problems at the compressor’s existing relief valve downstream pipes due to process condition changes after rotor change out. This paper covers high frequency acoustic excitation (HFAE) vibration also known as acoustic induced vibration (AIV) study and discusses detailed methodologies as a companion to the Energy Institute Guidelines for the avoidance of vibration induced fatigue failure, which is a common industry practice to assess and mitigate for AIV induced fatigue failure. Such detailed theoretical studies can help to minimize or totally avoid physical pipe modification, leading to reduce offshore plant shutdown days to plant shutdowns only being required to accommodate gas compressor upgrades, reducing cost without compromising process safety.

We report infrared spectra of nitromethane anion, CH 3 NO 2 − , in the region 700–2150 cm −1 , obtained by Ar predissociation spectroscopy and electron detachment spectroscopy. The data are interpreted in the framework of second-order vibrational perturbation theory based on coupled-cluster electronic structure calculations. The modes in the spectroscopic region studied here are mainly based on vibrations involving the heavier atoms; this work complements earlier studies on nitromethane anion that focused on the CH stretching region of the spectrum. Electron detachment begins at photon energies far below the adiabatic electron affinity due to thermal population of excited vibrational states

Energy harvesting for the purpose of powering low power electronic sensor systems has received explosive attention in the last few years. Most works using deterministic approaches focusing on using the piezoelectric effect to harvest ambient vibrationenergy have concentrated on cantilever beams at resonance using harmonic excitation. Here, using a stochastic approach, we focus on using a stack configuration and harvesting broadband vibrationenergy, a more practically available ambient source. It is assumed that the ambient base excitation is stationary Gaussian white noise, which has a constant power-spectral density across the frequency range considered. The mean power acquired from a piezoelectric vibration-based energy harvester subjected to random base excitation is derived using the theory of random vibrations. Two cases, namely the harvesting circuit with and without an inductor, have been considered. Exact closed-form expressions involving non-dimensional parameters of the electromechanical system have been given and illustrated using numerical examples

Energy harvesting for the purpose of powering low power electronic sensor systems has received explosive attention in the last few years. Most works using deterministic approaches focusing on using the piezoelectric effect to harvest ambient vibrationenergy have concentrated on cantilever beams at resonance using harmonic excitation. Here, using a stochastic approach, we focus on using a stack configuration and harvesting broadband vibrationenergy, a more practically available ambient source. It is assumed that the ambient base excitation is stationary Gaussian white noise, which has a constant power-spectral density across the frequency range considered. The mean power acquired from a piezoelectric vibration-based energy harvester subjected to random base excitation is derived using the theory of random vibrations. Two cases, namely the harvesting circuit with and without an inductor, have been considered. Exact closed-form expressions involving non-dimensional parameters of the electromechanical system have been given and illustrated using numerical examples.

at the University of Aalborg from 1988 to 1991. Secondly, a research project, In-Field Vibration Based Inspection of Civil Engineering Structures, which has been performed as a pilot project by the Consulting Engineers Rambøll, Hannemann and Højlund in cooperation with the department of Building Technology......The thesis has been written in relation to two different research projects. Firstly, an offshore test programme, Integrated Experimental/Numerical Analysis of the Dynamic behavior of offshore structures, which was performed at the department of Building Technology and Structural Engineering...... and Structural Engineering at the University of Aalborg since the beginning of 1992. Both projects have been supported by the Danish Technical Research Council. Further, the first mentioned project was supported by the Danish Energy Agency. Their financial support is gratefully acknowledged....

Spacecraft must withstand rigorous mechanical environment experiences such as acceleration, noise, vibration, and shock during the process of launching, satellite-vehicle separation, and so on. In this paper, a new spacecraft multifunctional structure concept designed by us is introduced. The multifunctional structure has the functions of not only load bearing, but also vibration reduction, energy source, thermal control, and so on, and we adopt a series of viscoelastic parts as connections b...

Full Text Available Over the past few years, remarkable developments in piezoelectric materials have motivated many researchers to work in the field of vibrationenergy harvesting by using piezoelectric beam like smart structures. This paper aimed to present the most recent application of a dual function piezoelectric device which can suppress vibration and harvest vibrationenergy simultaneously and a brief illustration of conventional mechanical and electrical TVAs (Tuned Vibration Absorber. It is shown that the proposed dual function device combines the benefits of conventional mechanical and electrical TVAs and reduces their relative disadvantages. Conversion of mechanical energy into electrical energy introduces damping and, hence, the optimal damping required by this TVA is generated by the energy harvesting effects. This paper presents the methodology of implementing the theory of 'electromechanical' TVAs to suppress the response of any real world structure. The work also illustrates the prospect of extensive applications of such novel "electromechanical" TVAs in defence and industry. The results show that the optimum degree of vibration suppression of an electronic box is achieved by this dual function TVA through suitable tuning of the attached electrical circuitry

Over the past few years, remarkable developments in piezoelectric materials have motivated many researchers to work in the field of vibrationenergy harvesting by using piezoelectric beam like smart structures. This paper aimed to present the most recent application of a dual function piezoelectric device which can suppress vibration and harvest vibrationenergy simultaneously and a brief illustration of conventional mechanical and electrical TVAs (Tuned Vibration Absorber). It is shown that the proposed dual function device combines the benefits of conventional mechanical and electrical TVAs and reduces their relative disadvantages. Conversion of mechanical energy into electrical energy introduces damping and, hence, the optimal damping required by this TVA is generated by the energy harvesting effects. This paper presents the methodology of implementing the theory of electromechanical TVAs to suppress the response of any real world structure. The work also illustrates the prospect of extensive applications of such novel electromechanical TVAs in defence and industry. The results show that the optimum degree of vibration suppression of an electronic box is achieved by this dual function TVA through suitable tuning of the attached electrical circuitry. (author)

The number of people passing through different indoor areas is useful in various smart structure applications, including occupancy-based building energy/space management, marketing research, security, etc. Existing approaches to estimate occupant traffic include vision-, sound-, and radio-based (mobile) sensing methods, which have placement limitations (e.g., requirement of line-of-sight, quiet environment, carrying a device all the time). Such limitations make these direct sensing approaches difficult to deploy and maintain. An indirect approach using geophones to measure floor vibration induced by footsteps can be utilized. However, the main challenge lies in distinguishing multiple simultaneous walkers by developing features that can effectively represent the number of mixed signals and characterize the selected features under different traffic conditions. This paper presents a method to monitor multiple persons. Once the vibration signals are obtained, features are extracted to describe the overlapping vibration signals induced by multiple footsteps, which are used for occupancy traffic estimation. In particular, we focus on analysis of the efficiency and limitations of the four selected key features when used for estimating various traffic conditions. We characterize these features with signals collected from controlled impulse load tests as well as from multiple people walking through a real-world sensing area. In our experiments, the system achieves the mean estimation error of +/-0.2 people for different occupant traffic conditions (from one to four) using k-nearest neighbor classifier.

The equilibrium bond lengths and binding energy, second differences in energy and vibrational frequencies of free clusters Nin (2 ≤ n ≤ 20) were calculated with the use of the interaction potential obtained in the tight-binding approximation (TBA). The results show that the minimum vibration frequency plays a significant role in the evaluation of the dynamic stability of the clusters. A nonmonotonic dependence of the minimum vibration frequency of clusters on their size and the extreme values for the number of atoms in a cluster n = 4, 6, 13, and 19 are demonstrated. This result agrees with the theoretical and experimental data on stable structures of small metallic clusters.

Full Text Available We present a new design strategy that makes it possible to synthesize decentralized output-feedback controllers by solving two successive optimization problems with linear matrix inequality (LMI constraints. In the initial LMI optimization problem, two auxiliary elements are computed: a standard state-feedback controller, which can be taken as a reference in the performance assessment, and a matrix that facilitates a proper definition of the main LMI optimization problem. Next, by solving the second optimization problem, the output-feedback controller is obtained. The proposed strategy extends recent results in static output-feedback control and can be applied to design complex passive-damping systems for vibrational control of large structures. More precisely, by taking advantages of the existing link between fully decentralized velocity-feedback controllers and passive linear dampers, advanced active feedback control strategies can be used to design complex passive-damping systems, which combine the simplicity and robustness of passive control systems with the efficiency of active feedback control. To demonstrate the effectiveness of the proposed approach, a passive-damping system for the seismic protection of a five-story building is designed with excellent results.

Full Text Available Spacecraft must withstand rigorous mechanical environment experiences such as acceleration, noise, vibration, and shock during the process of launching, satellite-vehicle separation, and so on. In this paper, a new spacecraft multifunctional structure concept designed by us is introduced. The multifunctional structure has the functions of not only load bearing, but also vibration reduction, energy source, thermal control, and so on, and we adopt a series of viscoelastic parts as connections between substructures. Especially in this paper, a vibration antiresonance design method is proposed to realize the vibration reduction. The complex zero-point equations of the vibration system are firstly established, and then the vibration antiresonance design for the system is achieved. For solving the difficulties due to viscoelastic characteristics of the connecting parts, we present the determining formulas to obtain the structural parameters, so that the complex zero-point equations can be satisfied. Numerical simulation and ground experiment demonstrate the correctness and effectiveness of the proposed method. This method can solve the structuralvibration control problem under the function constraints of load bearing and energy supplying and will expand the performance of spacecraft functional modules.

Ambient mechanical vibrations offer an attractive solution for powering the wireless sensor nodes of the emerging “Internet-of-Things”. However, the wide-ranging variability of the ambient vibration frequencies pose a significant challenge to the efficient transduction of vibration into usable electrical energy. This work reports the development of a MEMS electromagnetic vibrationenergy harvester where the resonance frequency of the oscillator can be adjusted or tuned to adapt to the ambient vibrational frequency. Micro-fabricated silicon spring and double layer planar micro-coils along with sintered NdFeB micro-magnets are used to construct the electromagnetic transduction mechanism. Furthermore, another NdFeB magnet is adjustably assembled to induce variable magnetic interaction with the transducing magnet, leading to significant change in the spring stiffness and resonance frequency. Finite element analysis and numerical simulations exhibit substantial frequency tuning range (25% of natural resonance frequency) by appropriate adjustment of the repulsive magnetic interaction between the tuning and transducing magnet pair. This demonstrated method of frequency adjustment or tuning have potential applications in other MEMS vibrationenergy harvesters and micromechanical oscillators.

Ambient mechanical vibrations offer an attractive solution for powering the wireless sensor nodes of the emerging “Internet-of-Things”. However, the wide-ranging variability of the ambient vibration frequencies pose a significant challenge to the efficient transduction of vibration into usable electrical energy. This work reports the development of a MEMS electromagnetic vibrationenergy harvester where the resonance frequency of the oscillator can be adjusted or tuned to adapt to the ambient vibrational frequency. Micro-fabricated silicon spring and double layer planar micro-coils along with sintered NdFeB micro-magnets are used to construct the electromagnetic transduction mechanism. Furthermore, another NdFeB magnet is adjustably assembled to induce variable magnetic interaction with the transducing magnet, leading to significant change in the spring stiffness and resonance frequency. Finite element analysis and numerical simulations exhibit substantial frequency tuning range (25% of natural resonance frequency) by appropriate adjustment of the repulsive magnetic interaction between the tuning and transducing magnet pair. This demonstrated method of frequency adjustment or tuning have potential applications in other MEMS vibrationenergy harvesters and micromechanical oscillators. (paper)

Development of new nanoscale devices has increased the demand for new types of small-scale energy resources such as ambient vibrationsenergy harvesters. Among the vibrationenergy harvesters, piezoelectric energy harvesters (PEHs) can be easily miniaturized and fabricated in micro and nano scales. This change in the dimensions of a PEH leads to a change in its governing equations of motion, and consequently, the predicted harvested energy comparing to a macroscale PEH. In this research, effects of small scale dimensions on the nonlinear vibration and harvested voltage of a nanoscale PEH is studied. The PEH is modeled as a cantilever piezoelectric bimorph nanobeam with a tip mass, using the Euler-Bernoulli beam theory in conjunction with Hamilton's principle. A harmonic base excitation is applied as a model of the ambient vibrations. The nonlocal elasticity theory is used to consider the size effects in the developed model. The derived equations of motion are discretized using the assumed-modes method and solved using the method of multiple scales. Sensitivity analysis for the effect of different parameters of the system in addition to size effects is conducted. The results show the significance of nonlocal elasticity theory in the prediction of system dynamic nonlinear behavior. It is also observed that neglecting the size effects results in lower estimates of the PEH vibration amplitudes. The results pave the way for designing new nanoscale sensors in addition to PEHs.

The application of energy harvesting technology for monitoring civil infrastructure is a bourgeoning topic of interest. The ability of kinetic energy harvesters to scavenge ambient vibrationenergy can be useful for large civil infrastructure under operational conditions, particularly for bridge structures. The experimental integration of such harvesters with full scale structures and the subsequent use of the harvested energy directly for the purposes of structural health monitoring shows promise. This paper presents the first experimental deployment of piezoelectric vibrationenergy harvesting devices for monitoring a full-scale bridge undergoing forced dynamic vibrations under operational conditions using energy harvesting signatures against time. The calibration of the harvesters is presented, along with details of the host bridge structure and the dynamic assessment procedures. The measured responses of the harvesters from the tests are presented and the use the harvesters for the purposes of structural health monitoring (SHM) is investigated using empirical mode decomposition analysis, following a bespoke data cleaning approach. Finally, the use of sequential Karhunen Loeve transforms to detect train passages during the dynamic assessment is presented. This study is expected to further develop interest in energy-harvesting based monitoring of large infrastructure for both research and commercial purposes.

Full Text Available Reducing the weight of the railway vehicles stands as a decisive rule in their design, entailed by higher velocities, the need to consume less energy and lower the manufacturing costs, along with the maximization of the use of loads on the axle. Once complied with this rule, the vehicle flexibility increases and leads to an easy excitation of the structuralvibrations in the carbody, with an impact upon the ride comfort in the railway vehicle. For a better ride comfort in lightweight railway vehicles, both vibration isolation approaches and structural damping approaches have been introduced. The paper herein submits a brief review of the main structural damping approaches aiming to reduce the amplitude in the carbody structuralvibrations, based on the use of the piezoelectric elements in passive control schemes. The paper outcomes show the potential of the presented methods concerning the reduction of the flexible vibrations in the carbody and the ride comfort improvement.

Active and Passive Vibration Control of Structures form an issue of very actual interest in many different fields of engineering, for example in the automotive and aerospace industry, in precision engineering (e.g. in large telescopes), and also in civil engineering. The papers in this volume bring together engineers of different background, and it fill gaps between structural mechanics, vibrations and modern control theory. Also links between the different applications in structural control are shown.

Full Text Available Bridge structure test results with using different types of dynamic force have been considered. It has been shown, that the developed technique of registering and processing vibration signals allows obtaining thin spectrum structure. The analysis of its change that is defined by the type of structure loading applied has been carried out. Key parameters of the vibration signals registered have been defined.

Some of the lingering challenges within the current paradigm of vibrationenergy harvesting (VEH) involve narrow operational frequency range and the inevitable non-resonant response from broadband noise excitations. Such VEHs are only suitable for limited applications with fixed sinusoidal vibration, and fail to capture a large spectrum of the real world vibration. Various arraying designs, frequency tuning schemes and nonlinear vibratory approaches have only yielded modest enhancements. To fundamentally address this, the paper proposes and explores the potentials in using highly nonlinear magnetic spring force to activate an autoparametric oscillator, in order to realize an inherently broadband resonant system. Analytical and numerical modelling illustrate that high spring nonlinearity derived from magnetic levitation helps to promote the 2:1 internal frequency matching required to activate parametric resonance. At the right internal parameters, the resulting system can intrinsically exhibit semi-resonant response regardless of the bandwidth of the input vibration, including broadband white noise excitation. (paper)

Vibrationenergy harvesting is an attractive technique for potential powering of wireless sensors and low power devices. While the technique can be employed to harvest energy from vibrations and vibratingstructures, a general requirement independent of the energy transfer mechanism is that the vibrationenergy harvesting device operate in resonance at the excitation frequency. Most energy harvesting devices developed to date are single resonance frequency based, and while recent efforts have been made to broaden the frequency range of energy harvesting devices, what is lacking is a robust tunable energy harvesting technique. In this paper, the design and testing of a resonance frequency tunable energy harvesting device using a magnetic force technique is presented. This technique enabled resonance tuning to ± 20% of the untuned resonant frequency. In particular, this magnetic-based approach enables either an increase or decrease in the tuned resonant frequency. A piezoelectric cantilever beam with a natural frequency of 26 Hz is used as the energy harvesting cantilever, which is successfully tuned over a frequency range of 22–32 Hz to enable a continuous power output 240–280 µW over the entire frequency range tested. A theoretical model using variable damping is presented, whose results agree closely with the experimental results. The magnetic force applied for resonance frequency tuning and its effect on damping and load resistance have been experimentally determined

Electromechanical devices that generate an electrical signal in response to an external source of mechanical vibrations can operate as a sensor of vibrations and as an energy harvester for converting mechanical vibration to electrical energy. The devices incorporate a magnet that is movable through a gap in a ferromagnetic circuit, wherein a coil is wound around a portion of the ferromagnetic circuit. A flexible coupling is used to attach the magnet to a frame for providing alignment of the magnet as it moves or oscillates through the gap in the ferromagnetic circuit. The motion of the magnet can be constrained to occur within a substantially linear range of magnetostatic force that develops due to the motion of the magnet. The devices can have ferromagnetic circuits with multiple arms, an array of magnets having alternating polarity and, encompass micro-electromechanical (MEM) devices.

Changes in the electronic structure of pigments in protein environments and of polar molecules in solution inevitably induce a re-adaption of molecular nuclear structure. Both changes of electronic and vibrationalenergies can be probed with visible or infrared lasers, such as two-dimensional electronic spectroscopy or vibrational spectroscopy. The extent to which the two changes are correlated remains elusive. The recent demonstration of two-dimensional electronic-vibrational (2DEV) spectroscopy potentially enables a direct measurement of this correlation experimentally. However, it has hitherto been unclear how to characterize the correlation from the spectra. In this paper, we present a theoretical formalism to demonstrate the slope of the nodal line between the excited state absorption and ground state bleach peaks in the spectra as a characterization of the correlation between electronic and vibrational transition energies. We also show the dynamics of the nodal line slope is correlated to the vibrational spectral dynamics. Additionally, we demonstrate the fundamental 2DEV spectral line-shape of a monomer with newly developed response functions.

vibrational spectra were compared with theoretical transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT). The results leave no doubt that the stable ground state configuration of TDBM corresponds to the intramolecularly hydrogen bonded enol form (e-CCC), and that the photoproduct corresponds...

Two identical full-scale 4-story reinforced concrete structures were built in 1965-1966 at the Nevada Test Site to investigate their dynamic response behavior to underground nuclear explosions. For eight years following their construction, the structures were the subject of a continuing program of vibration testing, and substantial data has been collected on the elastic response of these structures. In 1974 it was decided to conduct a high-amplitude vibration test that would cause the south structure (free of partitions) to deform beyond its elastic limit and cause major structural damage. Results of the 1974 testing program are summarized

A new device that combines vibration isolation and energy harvesting is modeled, simulated, and tested. The vibration isolating portion of the device uses post-buckled beams as its spring elements. Piezoelectric film is applied to the beams to harvest energy from their dynamic flexure. The entire device operates passively on applied base excitation and requires no external power or control system. The structural system is modeled using the elastica, and the structural response is applied as forcing on the electric circuit equation to predict the output voltage and the corresponding harvested power. The vibration isolation and energy harvesting performance is simulated across a large parameter space and the modeling approach is validated with experimental results. Experimental transmissibilities of 2% and harvested power levels of 0.36 μW are simultaneously demonstrated. Both theoretical and experimental data suggest that there is not necessarily a trade-off between vibration isolation and harvested power. That is, within the practical operational range of the device, improved vibration isolation will be accompanied by an increase in the harvested power as the forcing frequency is increased.

Vibrational fingerprints of small Pt(n)P(2n) (n = 1-5) clusters were computed from their low-lying structures located from a global exploration of their DFT potential energy surfaces with the GSAM code. Five DFT methods were assessed from the CCSD(T) wavenumbers of PtP2 species and CCSD relative energies of Pt2P4 structures. The eight first Pt(n)P(2n) isomers found are reported. The vibrational computations reveal (i) the absence of clear signatures made by overtone or combination bands due to very weak mechanical and electrical anharmonicities and (ii) some significant and recurrent vibrational fingerprints in correlation with the different PP bonding situations in the Pt(n)P(2n) structures.

The numerical method of design optimization for structural thermally induced vibration is originally studied in this paper and implemented in application software JIFEX. The direct and adjoint methods of sensitivity analysis for thermal induced vibration coupled with both linear and nonlinear transient heat conduction is firstly proposed. Based on the finite element method, the structural linear dynamics is treated simultaneously with coupled linear and nonlinear transient heat structural linear dynamics is treated simultaneously with coupled linear and nonlinear transient heat conduction. In the thermal analysis model, the nonlinear heat conduction considered is result from the radiation and temperature-dependent materials. The sensitivity analysis of transient linear and nonlinear heat conduction is performed with the precise time integration method. And then, the sensitivity analysis of structural transient dynamics is performed by the Newmark method. Both the direct method and the adjoint method are employed to derive the sensitivity equations of thermal vibration, and there are two adjoint vectors of structure and heat conduction respectively. The coupling effect of heat conduction on thermal vibration in the sensitivity analysis is particularly investigated. With coupling sensitivity analysis, the optimization model is constructed and solved by the sequential linear programming or sequential quadratic programming algorithm. The methods proposed have been implemented in the application software JIFEX of structural design optimization, and numerical examples are given to illustrate the methods and usage of structural design optimization on thermally induced vibration

Energy harvesting from ambient sources has been a longtime goal for microsystem engineers. The energy available from ambient sources is substantial and could be used to power wireless micro devices, making them fully autonomous. Self-powered wireless sensors could have many applications in for autonomous monitoring of residential, commercial, industrial, geological, or biological environments. Ambient vibrations are of particular interest for energy harvesting as they are ubiquitous and have ample kinetic energy. In this work a MEMS device for vibrationenergy harvesting using a variable capacitor structure is presented. The nonlinear electromechanical dynamics of a gap-closing type structure is experimentally studied. Important experimental considerations such as the importance of reducing off-axis vibration during testing, characterization methods, dust contamination, and the effect of grounding on parasitic capacitance are discussed. A comprehensive physics based model is developed and validated with two different microfabricated devices. To achieve maximal power, devices with high aspect ratio electrodes and a novel two-level stopper system are designed and fabricated. The maximum achieved power from the MEMS device when driven by sinusoidal vibrations was 3.38 muW. Vibrations from HVAC air ducts, which have a primary frequency of 65 Hz and amplitude of 155 mgrms, are targeted as the vibration source and devices are designed for maximal power harvesting potential at those conditions. Harvesting from the air ducts, the devices reached 118 nW of power. When normalized to the operating conditions, the best figure of merit of the devices tested was an order of magnitude above state-of-the-art of the devices (1.24E-6).

The stable conformers of trans-2-methoxycinnamic acid (trans-2MCA) are determined by potential energy profile analysis. The energies of the s-cis and s-trans conformers of trans-2MCA determined by B3LYP/cc-pVTZ method are -612.9788331 Hartrees and -612.9780953 Hartrees, respectively. The vibrational and electronic investigations of the stable s-cis and s-trans conformers of trans-2-methoxycinnamic acid have been carried out extensively with FTIR and FT-Raman spectral techniques. The s-cis conformer (I) with a (C16-C17-C18-O19) dihedral angle equal to 0° is found to be more favoured relative to the one s-trans (II) with (C16-C17-C18-O19) = 180°, possibly due to delocalization, hydrogen bonding and steric repulsion effects between the methoxy and acrylic acid groups. The DFT studies are performed with B3LYP method by utilizing 6-311++G** and cc-pVTZ basis sets to determine the structure, thermodynamic properties, vibrational characteristics and chemical shifts of the compound. The total dipole moments of the conformers determined by B3LYP/cc-pVTZ method are 3.35 D and 4.87 D for s-cis and s-trans, respectively. It reveals the higher polarity of s-trans conformer of trans-2MCA molecule. The electronic and steric influence of the methoxy group on the skeletal frequencies has been analysed. The energies of the frontier molecular orbitals and the LUMO-HOMO energy gap have been determined. The MEP of s-cis conformer lie in the range +1.374e × 10-2 to -1.374e × 10-2 while for s-trans it is +1.591e × 10-2 to -1.591e × 10-2. The total electron density of s-cis conformer lie in the range +5.273e × 10-2 to -5.273e × 10-2 while for s-trans it is +5.403e × 10-2 to -5.403e × 10-2. The MEP and total electron density shows that the s-cis conformer is less polar, less reactive and more stable than the s-trans conformer. All the reactivity descriptors of the molecule have been discussed. Intramolecular electronic interactions and their stabilisation energies have analysed

Reliable predictions of the dynamic loads and the lifetime of structures are inﬂuenced by the limited accuracy concerning the level of structural damping. The mechanisms of damping cannot be derived analytically from ﬁrst principles, and in the design of structures the damping is therefore based...... on experience or estimated from measurements. This thesis consists of an extended summary and three papers which focus on enhanced methods for identiﬁcation of damping from random struc-turalvibrations. The developed methods are validated by stochastic simulations, experimental data and full-scale measurements...... which are representative of the vibrations in small and large-scale structures. The ﬁrst part of the thesis presents an automated procedure which is suitable for estimation of the natural frequencies and the modal damping ratios from random response of structures. The method can be incorporated within...

Using Medium Energy Ion Scattering, we have studied the structural and vibrational properties of a number of clean and chemisorbed metal surfaces. The work presented in this thesis is mainly of a fundamental nature. However, it is believed that an atomistic understanding of the forces that affect surface structural and vibrational properties can have a beneficial impact on a large number of areas of applied nature. We find that the surface structure of Cu(001) follows the common trend for metal surfaces, where a small oscillatory relaxation exists beginning with a slight contraction in the top layer. In addition, the surface vibrational amplitude is enhanced (as s usually the case) by ∼80%. A detailed analysis of our data shows an unexpected anisotropy of the vibrational amplitude, such that the out-of-plane vibrational amplitude is 30% smaller than the in-plane vibrational amplitude. The unexpected results may imply a large tensile stress on Cu(001). Upon adsorption of 1/4 of a monolayer of S, a p(2 x 2)-S/Cu(001) surface is created. This submonolayer amount of S atoms makes the surface bulk-like, in which the anisotropy of the surface vibrations is removed and the first interlayer contraction is lifted. By comparing our model to earlier contradictory results on this controversial system. We find excellent agreement with a recent LEED study. The presence of 0.1 monolayer of Ca atoms on the Au(113) surface induces a drastic atomic rearrangements, in which half of the top layer Au atoms are missing and a (1 x 2) symmetry results. In addition, the first interlayer spacing of Au(113) is significantly reduced. Our results are discussed in terms of the energy balance between competing surface electronic charge densities

This study presents vibration-based structural health monitoring method in foundation-structure interface of harbor caisson structure. In order to achieve the objective, the following approaches are implemented. Firstly, vibration-based response analysis method is selected and structural health monitoring (SHM) technique is designed for harbor caisson structure. Secondly, the performance of designed SHM technique for harbor structure is examined by FE analysis. Finally, the applicability of designed SHM technique for harbor structure is evaluated by dynamic tests on a lab-scaled caisson structure.

Fascinating anisotropy decay experiments have recently been performed on H{sub 2}O ice Ih by Timmer and Bakker [R. L. A. Timmer, and H. J. Bakker, J. Phys. Chem. A 114, 4148 (2010)]. The very fast decay (on the order of 100 fs) is indicative of resonant energy transfer between OH stretches on different molecules. Isotope dilution experiments with deuterium show a dramatic dependence on the hydrogen mole fraction, which confirms the energy transfer picture. Timmer and Bakker have interpreted the experiments with a Förster incoherent hopping model, finding that energy transfer within the first solvation shell dominates the relaxation process. We have developed a microscopic theory of vibrational spectroscopy of water and ice, and herein we use this theory to calculate the anisotropy decay in ice as a function of hydrogen mole fraction. We obtain very good agreement with experiment. Interpretation of our results shows that four nearest-neighbor acceptors dominate the energy transfer, and that while the incoherent hopping picture is qualitatively correct, vibrationalenergy transport is partially coherent on the relevant timescale.

In a damping structure of a reactor building, an inner concrete body and a reactor container are connected by way of a vibration absorbing member. As the vibration absorbing member, springs or dampers are used. The inner concrete body and the reactor container each having weight and inherent frequency different from each other are opposed displaceably by way of the vibration absorbing member thereby enabling to reduce seismic input and reduce shearing force at least at leg portions. Accordingly, seismic loads are reduced to increase the grounding rate of the base thereby enabling to satisfy an allowable value. Therefore, it is not necessary to strengthen the inner concrete body and the reactor container excessively, the amount of reinforcing rods can be reduced, and the amount of a portion of the base buried to the ground can be reduced thereby enabling to constitute the reactor building easily. (N.H.)

A class of smart paint sensors is proposed for monitoring the structuralvibration of beams. The sensor is manufactured from an epoxy resin which is mixed with carbon black nano-particles to make it electrically conducting and sensitive to mechanical vibrations. A comprehensive theoretical and experimental investigation is presented to understand the underlying phenomena governing the operation of this class of paint sensors and evaluate its performance characteristics. A theoretical model is presented to model the electromechanical behavior of the sensor system using molecular theory. The model is integrated with an amplifier circuit in order to predict the current and voltage developed by the paint sensor when subjected to loading. Furthermore, the sensor/amplifier circuit models are coupled with a finite element model of a base beam to which the sensor is bonded. The resulting multi-field model is utilized to predict the behavior of both the sensor and the beam when subjected to a wide variety of vibration excitations. The predictions of the multi-field finite element model are validated experimentally and the behavior of the sensor is evaluated both in the time and the frequency domains. The performance of the sensor is compared with the performance of conventional strain gages to emphasize its potential and merits. The presented techniques are currently being extended to sensors that can monitor the vibration and structural power flow of two-dimensional structures. (paper)

We report our observations of localized structures in a thin layer of an emulsion subjected to vertical oscillations. We observe persistent holes, which are voids that span the layer depth, and kinks, which are fronts between regions with and without fluid. These structures form in response to a finite amplitude perturbation. Combining experimental and rheological measurements, we argue that the ability of these structures to withstand the hydrostatic pressure of the surrounding fluid is due to convection within their rim. For persistent holes the oscillatory component of the convection generates a normal stress which opposes contraction, while for kinks the steady component of the convection generates a shear stress which opposes the hydrostatic stress of the surrounding fluid.

We propose a polymer electret based energy harvesting device in order to extract energy from vibration sources with low acceleration. With MEMS technology, a silicon structure is fabricated which can resonate in 2D directions. Thanks to the excellent mechanical properties of the silicon material......, the proof mass could be successfully driven by an external vibrations with acceleration as low as 0.014g (∼0.14 m/s2). A root mean square (RMS) power output of 1.17μW under 0.014g RMS acceleration at 75Hz is measured when an optimal load of 20.3 MΩ is applied. The frequency response of the device is also...

Methods of performing down hole operations in a wellbore. A vibrational source is positioned within a tubular member such that an annulus is formed between the vibrational source and an interior surface of the tubular member. A fluid medium, such as high bulk modulus drilling mud, is disposed within the annulus. The vibrational source forms a fluid coupling with the tubular member through the fluid medium to transfer vibrationalenergy to the tubular member. The vibrationalenergy may be used, for example, to free a stuck tubular, consolidate a cement slurry and/or detect voids within a cement slurry prior to the curing thereof.

Vertically vibrated shear thickening particulate suspensions can support a free-standing interfaces oriented parallel to gravity. We find that shear thickening worm-like micellar solutions also support such vertical interfaces. Above a threshold in acceleration, the solution spontaneously accumulates into a labyrinthine pattern characterized by a well-defined vertical edge. The formation of vertical structures is of interest because they are unique to shear-thickening fluids, and they indicate the existence of an unknown stress bearing mechanism.

Piezoelectric transducers can be used to harvest electrical energy from structuralvibrations in order to power continuously operating condition monitoring systems local to where they operate. However, excessive vibrations can compromise the safe operation of mechanical systems. Therefore, absorbers are commonly used to control vibrations. With an integrated device, the mechanical energy that otherwise would be dissipated can be converted via piezoelectric transducers. Vibration absorbers are...

This paper is concerned with the comparison of two methods well suited for the prediction of the wideband response of built-up structures subjected to high-frequency vibrational excitation. The first method is sometimes called the vibrational conductivity method and the second one is rather known as the radiosity method in the field of acoustics, or the radiative energy transfer method. Both are based on quite similar physical assumptions i.e. uncorrelated sources, mean response and high-frequency excitation. Both are based on analogies with some equations encountered in the field of heat transfer. However these models do not lead to similar results. This paper compares the two methods. Some numerical simulations on a pair of plates joined along one edge are provided to illustrate the discussion.

Historically, piezoelectric vibrationenergy harvesters have been limited to operation at a single, structurally resonant frequency. A piezoceramic energy harvester, such as a bimorph beam, operating at structural resonance exchanges energy between dynamic and strain regimes. This energy exchange increases the coupling between piezoceramic deformation and electrical charge generation. Two BVEH mechanisms are presented that exploit strain energy management to reduce inertial forces needed to deform the piezoceramic, thus increasing the coupling between structural and electrical energy conversion over a broadband vibration spectrum. Broadband vibration excitation produces a non-sinusoidal electrical wave form from the BVEH device. An adaptive energy conversion circuit was developed that exploits a buck converter to capture the complex waveform energy in a form easily used by standard electrical components.

The identification, on-line and in near real-time, of the vibration frequencies, modes and amplitudes of selected key reactor structural components and the visual monitoring of these phenomena by nuclear power plant operating staff will serve to further the safety and control philosophy of nuclear systems and lead to design optimisation. The School of Nuclear Engineering has developed a data acquisition system for vibration detection and identification. The system is interfaced with the HIFAR research reactor of the Australian Atomic Energy Commission. The reactor serves to simulate noise and vibrational phenomena which might be pertinent in power reactor situations. The data acquisition system consists of a small computer interfaced with a digital correlator and a Fourier transform unit. An incremental tape recorder is utilised as a backing store and as a means of communication with other computers. A small analogue computer and an analogue statistical analyzer can be used in the pre and post computational analysis of signals which are received from neutron and gamma detectors, thermocouples, accelerometers, hydrophones and strain gauges. Investigations carried out to date include a study of the role of local and global pressure fields due to turbulence in coolant flow and pump impeller induced perturbations on (a) control absorbers, (B) fuel element and (c) coolant external circuit and core tank structure component vibrations. (Auth.)

A novel method of decentralized structuralvibration control is presented. The control is assumed to be realized by a semi-active device. The objective is to stabilize a vibrating system with the optimal rates of decrease of the energy. The controller relies on an easily implemented decentralized switched state-feedback control law. It uses a set of communication channels to exchange the state information between the neighboring subcontrollers. The performance of the designed method is validated by means of numerical experiments performed for a double cantilever system equipped with a set of elastomers with controlled viscoelastic properties. In terms of the assumed objectives, the proposed control strategy significantly outperforms the passive damping cases and is competitive with a standard centralized control. The presented methodology can be applied to a class of bilinear control systems concerned with smart structural elements.

Bistable vibrationenergy harvesters are attracting more and more interest because of their capability to scavenge energy over a large frequency band. The bistable effect is usually based on magnetic interaction or buckled beams. This paper presents a novel architecture based on amplified piezoelectric structures. This buckled spring–mass architecture allows the energy of the dynamic mass to be converted into electrical energy in the piezoelectric materials as efficiently as possible. Modeling and design are performed and a normalized expression of the harvester behavior is given. Chirp and band-limited noise excitations are used to evaluate the proposed harvester’s performances. Simulation and experimental results are in good agreement. A method of using a spectrum plot for investigating the interwell motion is presented. The effect of the electric load impedance matching strategy is also studied. Results and comparisons with the literature show that the proposed device combines a large bandwidth and a high power density. (paper)

The nonlinear behavior of mechanical joints is a confounding element in modeling the dynamic response of structures. Though there has been some progress in recent years in modeling individual joints, modeling the full structure with myriad frictional interfaces has remained an obstinate challenge. A strategy is suggested for structural dynamics modeling that can account for the combined effect of interface friction distributed spatially about the structure. This approach accommodates the following observations: (1) At small to modest amplitudes, the nonlinearity of jointed structures is manifest primarily in the energy dissipation - visible as vibration damping; (2) Correspondingly, measured vibration modes do not change significantly with amplitude; and (3) Significant coupling among the modes does not appear to result at modest amplitudes. The mathematical approach presented here postulates the preservation of linear modes and invests all the nonlinearity in the evolution of the modal coordinates. The constitutive form selected is one that works well in modeling spatially discrete joints. When compared against a mathematical truth model, the distributed dissipation approximation performs well.

Full Text Available Extracting energy from ambient vibration to power wireless sensor nodes has been an attractive area of research, particularly in the automotive monitoring field. This article reports the design, analysis and testing of a vibrationenergy harvesting device based on a miniature asymmetric air-spaced cantilever. The developed design offers high power density, and delivers electric power that is sufficient to support most wireless sensor nodes for structural health monitoring (SHM applications. The optimized design underwent three evolutionary steps, starting from a simple cantilever design, going through an air-spaced cantilever, and ending up with an optimized air-spaced geometry with boosted power density level. Finite Element Analysis (FEA was used as an initial tool to compare the three geometries’ stiffness (K, output open-circuit voltage (Vave, and average normal strain in the piezoelectric transducer (εave that directly affect its output voltage. Experimental tests were also carried out in order to examine the energy harvesting level in each of the three designs. The experimental results show how to boost the power output level in a thin air-spaced cantilever beam for energy within the same space envelope. The developed thin air-spaced cantilever (8.37 cm3, has a maximum power output of 2.05 mW (H = 29.29 μJ/cycle.

Real-time model predictive controller (MPC) implementation in active vibration control (AVC) is often rendered difficult by fast sampling speeds and extensive actuator-deformation asymmetry. If the control of lightly damped mechanical structures is assumed, the region of attraction containing the set of allowable initial conditions requires a large prediction horizon, making the already computationally demanding on-line process even more complex. Model Predictive Vibration Control provides insight into the predictive control of lightly damped vibratingstructures by exploring computationally efficient algorithms which are capable of low frequency vibration control with guaranteed stability and constraint feasibility. In addition to a theoretical primer on active vibration damping and model predictive control, Model Predictive Vibration Control provides a guide through the necessary steps in understanding the founding ideas of predictive control applied in AVC such as: · the implementation of ...

The pressure fluctuations generated by disturbed flows, encountered in nuclear reactors induce vibrations in the structures. In order to make forecastings for these vibrational levels, it is necessary to know the characteristics of the random pressure fluctuations induced in the walls by the main flow peculiarities of the circuits. This knowledge is essentially provided by experimentation which shows that most of the energy from these fluctuations is in the low frequency area. It is also necessary to determine the transfer functions of the fluid-structure coupled system. Given the frequency range of the excitations, a calculation of the characteristics of the first eigenmodes is generally sufficient. This calculation is carried out by finite element codes, the modal dampings being assessed separately. In this paper, emphasis is placed mainly on the analysis of the sources of excitation due to flow peculiarities. Some examples will also be given of assessments of vibrations in real structures (pipes, reactor internals, etc.) and of comparisons with the experimental results obtained on models or on a site [fr

Direct piezoelectric effect of Pb(Zr,Ti)O{sub 3} (PZT) thin films was investigated to discuss the application of ferroelectric films to vibrationenergy harvesting. From the model of the piezoelectric vibrationenergy harvester, it was found that the figure of merit (FOM) is proportional of the square of the effective transverse piezoelectric coefficient e{sub 31,f}. The e{sub 31,f} coefficient of PZT films were measured by substrate bending method. Furthermore, it was found that the e{sub 31,f} coefficient increases with increasing strain, which is favourable for the vibrationenergy harvesting.

Structuralvibration is a common phenomenon existing in various engineering fields such as machinery, aerospace, and civil engineering. It should be noted that the effective suppression of structuralvibration is conducive to enhancing machine performance, prolonging the service life of devices, and promoting the safety and comfort of structures. Conventional linear energy dissipative devices (linear dampers) are largely restricted for wider application owing to their low performance under certain conditions, such as the detuning effect of tuned mass dampers subjected to nonstationary excitations and the excessively large forces generated in linear viscous dampers at high velocities. Recently, nonlinear energy dissipative devices (nonlinear dampers) with broadband response and high robustness are being increasingly used in practical engineering. At the present stage, nonlinear dampers can be classified into three groups, namely nonlinear stiffness dampers, nonlinear-stiffness nonlinear-damping dampers, and nonlinear damping dampers. Corresponding to each nonlinear group, three types of nonlinear dampers that are widely utilized in practical engineering are reviewed in this paper: the nonlinear energy sink (NES), particle impact damper (PID), and nonlinear viscous damper (NVD), respectively. The basic concepts, research status, engineering applications, and design approaches of these three types of nonlinear dampers are summarized. A comparison between their advantages and disadvantages in practical engineering applications is also conducted, to provide a reference source for practical applications and new research.

The paper proposes a new piezoelectric smart structure with the integrated passive/active vibration-reduction performances, which is made of a series of periodic structural units. Every structural unit is made of two layers, one is an array of piezoelectric bimorphs (PBs) and one is an array of metal beams (MBs), both are connected as a whole by a metal plate. Analyses show that such a periodic smart structure possesses two aspects of vibration-reduction performance: one comes from its phonon crystal characteristics which can isolate those vibrations with the driving frequency inside the band gap(s). The other one comes from the electromechanical conversion of bent PBs, which is actively aimed at those vibrations with the driving frequency outside the band gap(s). By adjusting external inductance, the equivalent circuit of the proposed structure can be forced into parallel resonance such that most of the vibrationenergy is converted into electrical energy for dissipation by a resistance. Thus, an external circuit under the parallel resonance state is equivalent to a strong damping to the interrelated vibratingstructure, which is just the action mechanism of the active vibration reduction performance of the proposed smart structure.

Full Text Available Self-power supply is a promising project in various applied conditions. Among this research area, piezoelectric material-based energy harvesting (EH method has been researched in recent years due to its advantages. With the limitation of energy form acceptance range of EH circuit system, a sum of energy is not accessible to be obtained. To enlarge the EH quantity from the vibration, an enhanced piezoelectric vibration EH structure with piezoelectric film is developed in this work. Piezoelectric-based energy harvesting mechanism is primarily proposed in this work. The special-designed electric circuit for EH from macro fiber composite (MFC is proposed and then analyzed. When the structurevibrates in its modes of frequencies, the experiments are developed to measure the EH effect. The energy harvested from the vibratingstructure is analyzed and the enhanced effect is presented. The results indicate that, with the enhanced EH structure in this work, vibrationenergy from structure is obtained in a larger range, and the general EH quantity is enlarged.

Collisional energy transfer parameters for highly vibrationally excited azulene have been deduced from new infrared fluorescence (IRF) emission lifetime data with an improved calibration relating IRF intensity to vibrationalenergy [J. Shi, D. Bernfeld, and J. R. Barker, J. Chem. Phys. 88, XXXX (1988), preceding paper]. In addition, data from previous experiments [M. J. Rossi, J. R. Pladziewicz, and J. R. Barker, J. Chem. Phys. 78, 6695 (1983)] have been reanalyzed based on the improved calibration. Inversion of the IRF decay curves produced plots of energy decay, which were analyzed to determine , the average energy transferred per collision. Master equation simulations reproduced both the original IRF decays and the deduced energy decays. A third (simple) method of determination agrees well with the other two. The results show to be nearly directly proportional to the vibrationalenergy of the excited azulene from ∼8000 to 33 000 cm -1 . At high energies, there are indications that the energy dependence may be slightly reduced

IR pump-probe spectroscopy is used to study the effect of hydrogen bonding on the vibrationalenergy relaxation pathways. Hydrogen bonding accelerates the population relaxation from 12ps in diluted acetonitrile solution to 700fs in bulk water.

Full Text Available This paper presents a novel piezoelectric vibrationenergy harvester (PVEH in which a high-frequency generating beam (HFGB is driven by an array of low-frequency driving beams (LFDBs using ropes. Two mechanisms based on frequency upconversion and multimodal harvesting work together to broaden the frequency bandwidth of the proposed vibrationenergy harvester (VEH. The experimental results show that the output power of generating beam (GB remains unchanged with the increasing number of driving beams (DBs, compared with the traditional arrays of beams vibrationenergy harvester (AB-VEH, and the output power and bandwidth behavior can be adjusted by parameters such as acceleration, rope margin, and stiffness of LFDBs, which shows the potential to achieve unlimited wideband vibrationenergy-harvesting for a variable environment.

In the application of Statistical Energy Analysis "SEA" to complex assembled structures, a purely predictive model often exhibits errors. These errors are mainly due to a lack of accurate modelling of the power transmission mechanism described through the Coupling Loss Factors (CLF). Experimental SEA (ESEA) is practically used by the automotive and aerospace industry to verify and update the model or to derive the CLFs for use in an SEA predictive model when analytical estimates cannot be made. This work is particularly motivated by the lack of procedures that allow an estimate to be made of the variance and confidence intervals of the statistical quantities when using the ESEA technique. The aim of this paper is to introduce procedures enabling a statistical description of measured power input, vibrationenergies and the derived SEA parameters. Particular emphasis is placed on the identification of structural CLFs of complex built-up structures comparing different methods. By adopting a Stochastic Energy Model (SEM), the ensemble average in ESEA is also addressed. For this purpose, expressions are obtained to randomly perturb the energy matrix elements and generate individual samples for the Monte Carlo (MC) technique applied to derive the ensemble averaged CLF. From results of ESEA tests conducted on an aircraft fuselage section, the SEM approach provides a better performance of estimated CLFs compared to classical matrix inversion methods. The expected range of CLF values and the synthesized energy are used as quality criteria of the matrix inversion, allowing to assess critical SEA subsystems, which might require a more refined statistical description of the excitation and the response fields. Moreover, the impact of the variance of the normalized vibrationenergy on uncertainty of the derived CLFs is outlined.

The molecular mechanism responsible for the a component of exchange-type chromosome aberrations, of chromosome fragmentation and of reproductive cell death is one of the unsolved issues of radiation biology. Under review is whether vibrationalenergy relaxation in the constitutive biopolymers of chromatin, induced by inelastic energy deposition events and mediated via highly excited vibrational states, may provide a pathway of fast local chromatin denaturation, thereby producing the severe DNA lesion able to interact chemically with other, non-damaged chromatin. (author)

Basically, many major structures across the world such as towers, high rise building, houses and bridges utilize pile as a support material. The use of pile is important to strengthen the structures. However, this has led to another problem to the nearest surrounding structures resulted from pile driving. As part of a construction work, unavoidable pile driving activity generates a vibration towards the surrounding structures if uncontrolled may cause damage to the adjacent structure. As the current construction works are frequently located in urban areas where the distance between the nearest building structures is not far, vibration may cause damage to nearby structures. Knowing which part of the building that is mostly affected by various vibration patterns from the impact of pile driving is crucial. Thus, it is very important to predict the impact of vibration during piling installation work. This paper reviews the vibrations generated by piling activity toward surrounding structures in terms sources of vibration, impact of piling installation, pile-soil interaction, and factors affecting the vibration impact of building as well as to study the parameters involved in vibration generation during piling works.

Room temperature photoacoustic spectra in the region of the first through the fourth overtones (2ν 1 to 5ν 1 ) and free-jet action spectra of the second through the fourth overtones (3ν 1 to 5ν 1 ) of the N - H stretching vibration permit analysis of the vibrational and rotational structure of HNCO. The analysis identifies the strong intramolecular couplings that control the early stages of intramolecular vibrationalenergy redistribution (IVR) and gives the interaction matrix elements between the zero-order N - H stretching states and the other zero-order states with which they interact. The experimentally determined couplings and zero-order state separations are consistent with ab initio calculations of East, Johnson, and Allen [J. Chem. Phys. 98, 1299 (1993)], and comparison with the calculation identifies the coupled states and likely interactions. The states most strongly coupled to the pure N - H stretching zero-order states are ones with a quantum of N - H stretching excitation (ν 1 ) replaced by different combinations of N - C - O asymmetric or symmetric stretching excitation (ν 2 or ν 3 ) and trans-bending excitation (ν 4 ). The two strongest couplings of the nν 1 state are to the states (n-1)ν 1 +ν 2 +ν 4 and (n-1)ν 1 +ν 3 +2ν 4 , and sequential couplings through a series of low order resonances potentially play a role. The analysis shows that if the pure N - H stretch zero-order state were excited, energy would initially flow out of that mode into the strongly coupled mode in 100 fs to 700 fs, depending on the level of initial excitation. copyright 1999 American Institute of Physics

This book provides a comprehensive discussion of nonlinear multi-modal structuralvibration problems, and shows how vibration suppression can be applied to such systems by considering a sample set of relevant control techniques. It covers the basic principles of nonlinear vibrations that occur in flexible and/or adaptive structures, with an emphasis on engineering analysis and relevant control techniques. Understanding nonlinear vibrations is becoming increasingly important in a range of engineering applications, particularly in the design of flexible structures such as aircraft, satellites, bridges, and sports stadia. There is an increasing trend towards lighter structures, with increased slenderness, often made of new composite materials and requiring some form of deployment and/or active vibration control. There are also applications in the areas of robotics, mechatronics, micro electrical mechanical systems, non-destructive testing and related disciplines such as structural health monitoring. Two broader ...

Explicit evidence for the role of methyl rotor levels in promoting energy dispersal is reported. A set of coupled zero-order vibration/vibration-torsion (vibtor) levels in the S 1 state of para -fluorotoluene ( p FT) are investigated. Two-dimensional laser-induced fluorescence (2D-LIF) and two-dimensional zero-kinetic-energy (2D-ZEKE) spectra are reported, and the assignment of the main features in both sets of spectra reveals that the methyl torsion is instrumental in providing a route for coupling between vibrational levels of different symmetry classes. We find that there is very localized, and selective, dissipation of energy via doorway states, and that, in addition to an increase in the density of states, a critical role of the methyl group is a relaxation of symmetry constraints compared to direct vibrational coupling.

Many people are exposed to whole-body vibration (WBV) in their occupational lives, especially drivers of vehicles such as tractor and trucks. The main categories of effects from WBV are perception degraded comfort interference with activities-impaired health and occurrence of motion sickness. Absorbed power is defined as the power dissipated in a mechanical system as a result of an applied force. The vibration-induced injuries or disorders in a substructure of the human system are primarily associated with the vibration power absorption distributed in that substructure. The vibration power absorbed by the exposed body is a measure that combines both the vibration hazard and the biodynamic response of the body. The article presents measurement method for determining vibration power dissipated in the human whole body system called VibrationEnergy Absorption (VEA). The vibration power is calculated from the real part of the force-velocity cross-spectrum. The absorbed power in the frequency domain can be obtained from the cross-spectrum of the force and velocity. In the context of the vibrationenergy transferred to a seated human body, the real component reflects the energy dissipated in the biological structure per unit of time, whereas the imaginary component reflects the energy stored/released by the system. The seated human is modeled as a series/parallel 4-DOF dynamic models. After introduction of the excitation, the response in particular segments of the model can be analyzed. As an example, the vibration power dissipated in an operator has been determined as a function of the agricultural combination operating speed 1.39 - 4.16 ms(-1).

Full Text Available Many people are exposed to whole-body vibration (WBV in their occupational lives, especially drivers of vehicles such as tractor and trucks. The main categories of effects from WBV are perception degraded comfort interference with activities-impaired health and occurrence of motion sickness. Absorbed power is defined as the power dissipated in a mechanical system as a result of an applied force. The vibration-induced injuries or disorders in a substructure of the human system are primarily associated with the vibration power absorption distributed in that substructure. The vibration power absorbed by the exposed body is a measure that combines both the vibration hazard and the biodynamic response of the body. The article presents measurement method for determining vibration power dissipated in the human whole body system called VibrationEnergy Absorption (VEA. The vibration power is calculated from the real part of the force-velocity cross-spectrum. The absorbed power in the frequency domain can be obtained from the cross-spectrum of the force and velocity. In the context of the vibrationenergy transferred to a seated human body, the real component reflects the energy dissipated in the biological structure per unit of time, whereas the imaginary component reflects the energy stored/released by the system. The seated human is modeled as a series/parallel 4-DOF dynamic models. After introduction of the excitation, the response in particular segments of the model can be analyzed. As an example, the vibration power dissipated in an operator has been determined as a function of the agricultural combination operating speed 1.39 – 4.16 ms[sup] -1 [/sup].

The crystal structure of isoproturon [ N-(4-isopropylphenyl)- N', N'-dimethylurea] has been determined: the compound crystallizes in the space group Pbca with unit cell parameters a=10.186(2) Å, b=11.030(2) Å, c=20.981(4) Å. The structure was solved and refined down to R1=0.0508 and ωR2=0.12470 for 3056 reflections. The crystalline molecular network of this pesticide is stabilized, as for many molecules of the same family, by π-π interactions but especially by a medium-strong N-H&ctdot;C dbnd6 O intermolecular hydrogen bond (2.14 Å). The X-ray parameters were then compared with the results of DFT quantum chemical calculation computed with the GAUSSIAN 94 package. A tentative assignment of the ATR-FT-IR and Raman spectra was proposed supported by vibrational mode calculation and spectroscopic data on benzenic and urea derivatives available in the literature. The presence of a tight band around 3300 cm -1, which can be assigned to the NH bond stretching mode as well as the low frequency position of the amide I band at 1640 cm -1, sensitive to solvent polarity, confirms the existence of a quite strong intermolecular hydrogen bond between neighboring molecules in the crystal of isoproturon.

Full Text Available We propose a two-step strategy for the design of passive controllers for the simultaneous confinement and suppression of vibrations (SCSV in mechanical structures. Once the sensitive and insensitive elements of these structures are identified, the first design step synthesizes an active control law, which is referred to as the reference control law (RCL, for the SCSV. We show that the problem of SCSV can be formulated as an LQR-optimal control problem through which the maximum amplitudes, associated with the control input and the displacements of the sensitive and insensitive parts, can be regulated. In the second design step, a transformation technique that yields an equivalent passive controller is used. Such a technique uses the square root of sum of squares method to approximate an equivalent passive controller while maximizing the effects of springs and dampers characterizing passive elements that are added to the original structure. The viability of the proposed control design is illustrated using a three-DOF mechanical system subject to an excitation. It is assumed that all of the masses are sensitive to the excitation, and thus the vibratory energy must be confined in the added passive elements (insensitive parts. We show that the vibration amplitudes associated with the sensitive masses are attenuated at fast rate at the expense of slowing down the convergence of the passive elements to their steady states. It is also demonstrated that a combination of the RCL and the equivalent passive control strategy leads to similar structural performance.

Full Text Available A rigid circular cylinder with two piezoelectric beams attached on has been tested through vortex-induced vibrations (VIV and wake-induced vibrations (WIV by installing a big cylinder fixed upstream, in order to study the influence of the different flow-induced vibrations (FIV types. The VIV test shows that the output voltage increases with the increases of load resistance; an optimal load resistance exists for the maximum output power. The WIV test shows that the vibration of the small cylinder is controlled by the vortex frequency of the large one. There is an optimal gap of the cylinders that can obtain the maximum output voltage and power. For a same energy harvesting device, WIV has higher power generation capacity; then the piezoelectric output characteristics can be effectively improved.

Full Text Available Large amplitudes and attenuating vibration periods result in fatigue, instability, and poor structural performance. In light of past approaches in this field, this paper intends to discuss some innovative approaches in vibration control of intelligent structures, particularly in the case of structures with embedded piezoelectric materials. Control strategies are presented, such as the linear quadratic control theory, as well as more advanced theories, such as robust control theory. The paper presents sufficiently a recognizable advance in knowledge of active vibration control in intelligent structures.

Full Text Available In technical applications it takes place the problem of vibration damping in certain regions of the structure, at the location of optical sensors for instance, at any external dynamic excitations with no mass increase and no changes in spectral portrait. In order to solve these problems it is widespread the use of special damping devices: piezoelectric elements connected to external electric circuits and attached to the structure. It became possible due to piezoelectric effect, which provides transformation of part of energy of vibrations into electric one, which is dissipated in external electric circuit. So that by using appropriate electric circuits one may dissipate internal energy and therefore reduce structuralvibrations in definite frequency range. As a rule, external circuit of single branch, which shunts single piezoelectric element, allows vibration damping on one certain frequency. Due to the fact, that practical applications usually include requirements of damping of several modes by one and the same technical devices, the problem of multimodal vibration damping in smart-structures is rather acute. The objective of this paper is the study of possibility of vibration damping on several modes by using single external series RL-circuit, connected to electrodes of single piezoelectric element on the basis of solution of problems on natural and forced steady-state vibrations of electroelastic systems with external electric circuits.

The main aim of this paper is to present a systematic and structured approach to piping vibration assessment and control. Piping vibration assessment is a complex subject, since there are no general analytical methods for dealing with vibration problems. It was noted that most existing vibrating piping systems had poor or degraded support arrangements. This approach therefore focuses mainly on vibration control through assessing and improving the supporting systems. Vibration theory has not been covered in any detail. A simplified procedure is presented for the Integrity custodian to determine when a simple assessment may be carried out and when specialist/consultant services are required. The assessment techniques are based on simplifying assumptions, good rules of thumb and available literature and current practices. A typical case study is used to illustrate the use and the flexibility of the above approach. A standard sheet is proposed to record and document the assessment and recommendations

The vibration of a Francis turbine is analyzed with the additional quality matrix method based on fluid-structure coupling (FSC). Firstly, the vibration frequency and mode of blade and runner in air and water are calculated. Secondly, the influences to runner frequency domain by large flow, small flow and design flow working conditions are compared. Finally the influences to runner modes by centrifugal forces under three rotating speeds of 400 r/min, 500 r/min and 600 r/min are compared. The centrifugal force and small flow working condition have greatly influence on the vibration of small runner. With the increase of centrifugal force, the vibration frequency of the runner is sharply increased. Some order frequencies are even close to the runner natural frequency in the air. Because the low frequency vibration will severely damage the stability of the turbine, low frequency vibration of units should be avoided as soon as possible.

Flow-induced vibration is a term to denote those phenomena associated with the response of structures placed in or conveying fluid flow. More specifically, the terra covers those cases in which an interaction develops between fluid-dynamic forces and the inertia, damping or elastic forces in the structures. The study of these phenomena draws on three disciplines: (1) structural mechanics, (2) mechanical vibration, and (3) fluid dynamics. The vibration of circular cylinders subject to flow has been known to man since ancient times; the vibration of a wire at its natural frequency in response to vortex shedding was known in ancient Greece as aeolian tones. But systematic studies of the problem were not made until a century ago when Strouhal established the relationship between vortex shedding frequency and flow velocity for a given cylinder diameter. The early research in this area has beer summarized by Zdravkovich (1985) and Goldstein (1965). Flow-induced structuralvibration has been experienced in numerous fields, including the aerospace industry, power generation/transmission (turbine blades, heat exchanger tubes, nuclear reactor components), civil engineering (bridges, building, smoke stacks), and undersea technology. The problems have usually been encountered or created accidentally through improper design. In most cases, a structural or mechanical component, designed to meet specific objectives, develops problems when the undesired effects of flow field have not been accounted for in the design. When a flow-induced vibration problem is noted in the design stage, the engineer has different options to eliminate the detrimental vibration. Unfortunately, in many situations, the problems occur after the components are already in operation; the "fix" usually is very costly. Flow-induced vibration comprises complex and diverse phenomena; subcritical vibration of nuclear fuel assemblies, galloping of transmission lines, flutter of pipes conveying fluid, and whirling

Electromagnetic vibration transducers are seen as an effective way of harvesting ambient energy for the supply of sensor monitoring systems. Different electromagnetic coupling architectures have been employed but no comprehensive comparison with respect to their output performance has been carried out up to now. Electromagnetic VibrationEnergy Harvesting Devices introduces an optimization approach which is applied to determine optimal dimensions of the components (magnet, coil and back iron). Eight different commonly applied coupling architectures are investigated. The results show that correct dimensions are of great significance for maximizing the efficiency of the energy conversion. A comparison yields the architectures with the best output performance capability which should be preferably employed in applications. A prototype development is used to demonstrate how the optimization calculations can be integrated into the design–flow. Electromagnetic VibrationEnergy Harvesting Devices targets the design...

Because of the nonlinearity of the equation that governs flow, sometimes vibration occurs in an unexpected system, and it causes trouble. This 7th workshop on vibration related to fluid in atomic energy field was held at Nuclear Engineering Research Laboratory of University of Tokyo on August 25 and 26, 1997. Two themes were ``Vibration of liquid surface by flow`` and ``Numerical analysis of coupled vibration of fluid-structures``. The former is related to the problem in the development of a demonstration FBR, and the latter is related to the numerical analysis technology such as the handling of boundary conditions and the method of taking position, moving velocity and acceleration into account. This workshop aims at thoroughly discussing a small number of themes, and deepening the understanding. In this report, the summaries of 17 papers are collected, of which the titles are as follows. Liquid surface self-exciting vibration by flow, vibration of upper plenum liquid surface of fast reactor, stability analysis of multiple liquid surfaces, flow instability phenomena of multi-loop system, sloshing in a vessel in which fluid flows, the mechanism of occurrence of self-exciting sloshing in a vessel elucidated by numerical analysis, numerical analysis of manometer vibration excited by flow, numerical analysis of flutter phenomena of aircraft, numerical analysis of aerodynamic elastic problem, mechanism of in-line excitation, numerical analysis of hydrodynamic elastic vibration of tube nest and so on. (K.I.)

Population growth and urbanization results in densified cities, where new buildings are being built closer to existing vibration sources such as road-, tram- and rail traffic. In addition, new transportation systems are constructed closer to existing buildings. Potential disturbing vibrations...... are one issue to consider in planning urban environment and densification of cities. Vibrations can be disturbing for humans but also for sensitive equipment in, for example, hospitals. In determining the risk for disturbing vibrations, the distance between the source and the receiver, the ground...... properties, and type and size of the building are governing factors. In the paper, a study is presented aiming at investigating the influence of various parameters of the building's structural design on vibration levels in the structure caused by ground surface loads, e.g. traffic. Parameters studied...

Full Text Available For RV reducer widely used in robots, vibration significantly affects its performance. A lumped parameter model is developed to investigate free vibration characteristics without and with gyroscopic effects. The dynamic model considers key factors affecting vibration such as involute and cycloid gear mesh stiffness, crankshaft bending stiffness, and bearing stiffness. For both nongyroscopic and gyroscopic systems, free vibrations are examined and compared with each other. Results reveal the specific structure of vibration modes for both systems, which results from symmetry structure of RV reducer. According to vibration of the central components, vibration modes of two systems can be classified into three types, rotational, translational, and planetary component modes. Different from nongyroscopic system, the eigenvalues with gyroscopic effects are complex-valued and speed-dependent. The eigenvalue for a range of carrier speeds is obtained by numerical simulation. Divergence and flutter instability is observed at speeds adjacent to critical speeds. Furthermore, the work studies effects of key factors, which include crankshaft eccentricity and the number of pins, on eigenvalues. Finally, experiment is performed to verify the effectiveness of the dynamic model. The research of this paper is helpful for the analysis on free vibration and dynamic design of RV reducer.

An explicit time dependent approach for simultaneous VT and VV energy transfer in diatom--diatom collisions is explored using the exponential form of ladder operators in the solution of the Schroedinger equation of motion. The collision of two hydrogen molecules is chosen to illustrate the extent of interference between VT and VV modes among various vibrational states. While vibrationalenergy transfer processes of nominally VT type can be treated with pure VT mode at low collision energies, the intermode coupling is found to be very important at collision energies of several hω. The occurrence of the coupling appears to be nearly universal in vibrational transitions at such energies. Exceptions to the coupling have been discussed

Full Text Available This paper focuses on several aspects extending the dynamical efficiency of a cantilever beam vibrating in the third mode. A few ways of producing this mode stimulation, namely vibro-impact or forced excitation, as well as its application for energy harvesting devices are proposed. The paper presents numerical and experimental analyses of novel structural dynamics effects along with an optimal configuration of the cantilever beam. The peculiarities of a cantilever beam vibrating in the third mode are related to the significant increase of the level of deformations capable of extracting significant additional amounts of energy compared to the conventional harvester vibrating in the first mode. Two types of a piezoelectric vibratingenergy harvester (PVEH prototype are analysed in this paper: the first one without electrode segmentation, while the second is segmented using electrode segmentation at the strain nodes of the third vibration mode to achieve effective operation at the third resonant frequency. The results of this research revealed that the voltage generated by any segment of the segmented PVEH prototype excited at the third resonant frequency demonstrated a 3.4–4.8-fold increase in comparison with the non-segmented prototype. Simultaneously, the efficiency of the energy harvester prototype also increased at lower resonant frequencies from 16% to 90%. The insights presented in the paper may serve for the development and fabrication of advanced piezoelectric energy harvesters which would be able to generate a considerably increased amount of electrical energy independently of the frequency of kinematical excitation.

This process consists in exciting A molecules by absorption of a pulsed light beam, then in exciting until their dissociation X molecules, present in several isotopic forms, by a vibrational transfer between the A molecules and the X molecules, the A molecules having a dissociation energy greater than that of the X molecules, the duration and energy of the light pulses being such that the absorption time by the A molecules is less than the excitation time of the X molecules and the temperature conditions such that the thermal width of the vibration rays is at the most near the isotopic difference between the resonance rays of the two isotopic varieties [fr

Structuralvibrations induced by actuators can be minimized using input shaping. Input shaping is a feedforward method in which actuator commands are convolved with shaping functions to yield a shaped set of commands. These commands are designed to perform the maneuver while minimizing the residual structuralvibration. In this report, input shaping is extended to stepper motor actuators. As a demonstration, an input-shaping technique based on pole-zero cancellation was used to modify the Solar Array Drive Assembly (SADA) actuator commands for the Lewis satellite. A series of impulses were calculated as the ideal SADA output for vibration control. These impulses were then discretized for use by the SADA stepper motor actuator and simulated actuator outputs were used to calculate the structural response. The effectiveness of input shaping is limited by the accuracy of the knowledge of the modal frequencies. Assuming perfect knowledge resulted in significant vibration reduction. Errors of 10% in the modal frequencies caused notably higher levels of vibration. Controller robustness was improved by incorporating additional zeros in the shaping function. The additional zeros did not require increased performance from the actuator. Despite the identification errors, the resulting feedforward controller reduced residual vibrations to the level of the exactly modeled input shaper and well below the baseline cases. These results could be easily applied to many other vibration-sensitive applications involving stepper motor actuators.

Piezoelectric vibrationenergy harvesting (PVEH) has received much attention as a potential solution that could ultimately realize self-powered wireless sensor networks. Since most ambient vibrations in nature are inherently random and nonstationary, the output performances of PVEH devices also randomly change with time. However, little attention has been paid to investigating the randomly time-varying electroelastic behaviors of PVEH systems both analytically and experimentally. The objective of this study is thus to make a step forward towards a deep understanding of the time-varying performances of PVEH devices under nonstationary random vibrations. Two typical cases of nonstationary random vibration signals are considered: (1) randomly-varying amplitude (amplitude modulation; AM) and (2) randomly-varying amplitude with randomly-varying instantaneous frequency (amplitude and frequency modulation; AM-FM). In both cases, this study pursues well-balanced correlations of analytical predictions and experimental observations to deduce the relationships between the time-varying output performances of the PVEH device and two primary input parameters, such as a central frequency and an external electrical resistance. We introduce three correlation metrics to quantitatively compare analytical prediction and experimental observation, including the normalized root mean square error, the correlation coefficient, and the weighted integrated factor. Analytical predictions are in an excellent agreement with experimental observations both mechanically and electrically. This study provides insightful guidelines for designing PVEH devices to reliably generate electric power under nonstationary random vibrations.

This paper is divided into two parts concerning piping systems and a nuclear fuel pin system. The significant experimental results concerning the random vibration induced in an L-shaped pipe by air-water two-phase flow and the theoretical analysis of the vibration are described in the first part. It was clarified for the first time that the parametric excitation due to the periodic changes of system mass, centrifugal force and Coriolis force was the mechanism of exciting the vibration. Moreover, the experimental and theoretical analyses of the mechanism of exciting vibration by air-water two-phase flow in a straight, horizontal pipe were carried out, and the first natural frequency of the piping system was strongly related to the dominant frequency of void signals. The experimental results on the vibration of a nuclear fuel pin model in parallel air-water two-phase flow are reported in the latter part. The relations between vibrational strain variance and two-phase flow velocity or pressure fluctuation, and the frequency characteristics of vibrational strain variance were obtained. The theoretical analysis of the dynamic interaction between air-water two-phase flow and a fuel pin structure, and the vibrational instability of fuel pins in alternate air and water slugs or in large bubble flow are also reported. (Kako, I.)

In this paper we investigate the capability of harvesting the electric energy from mechanical vibrations in a dynamic environment through a piezoelectric membrane transducer. This transducer consists of 2 layers lead zirconate titanate (PZT)/brass, the brass layer is embedded over the whole circumference by epoxy adhesive. A very small vibration gives a consequent deformation of the membrane which generates electric energy. Due to the impedance matrices connecting the efforts and flows of the membrane, we have established the dynamic electric equivalent circuit of the transducer. In a first study and in order to validate theoretical results, we performed experiments with a vibrating machine moving a macroscopic 25 mm diameter piezoelectric membrane. A power of 1.8 mW was generated at the resonance frequency (2.58 kHz) across a 56 k{omega} optimal resistor and for a 2 g acceleration. (authors)

In this paper, we present a vibrationenergy harvester using magnetoelectric laminate composite and a springless spherical permanent magnet as a proof mass. The harvester utilizes a freely movable spherical permanent magnet to transform external vibration into a time varying magnetic field applied to the magnetoelectric transducer. The laminate composite consists of a Ni–Mn–Ga-based MSMA (magnetic shape memory alloy) element and a PZT (lead zirconate titanate) plate. A proof-of-concept harvester has been fabricated and characterized at various input accelerations and frequencies. A maximum open circuit voltage of 1.18 V has been obtained in response to a 3g vibration at 17 Hz with the fabricated device. Moreover, a maximum output voltage of 10.24 V and output power of 4.1 μW have been achieved on a 950 Ω load, when the fabricated energy harvester was mounted on a smartphone and shaken by hand. (paper)

The vibrational spectra of different uranyl compounds has been studied and of it spectral information has been used the fundamental asymmetric vibrational frequency, to determine the length and constant bond force U=O by means of the combination of the concept of absorbed energy and the mathematical expression of Badger modified by Jones. It is intended a factor that simplifies the mathematical treatment and the results are compared with the values obtained for other methods. (Author)

This paper reviews the design, implementation, and demonstration of energy harvesting devices that exploit flow-induced vibrations as the main source of energy. Starting with a presentation of various concepts of energy harvesters that are designed to benefit from a general class of flow-induced vibrations, specific attention is then given at those technologies that may offer, today or in the near future, a potential benefit to extend the operational capabilities and to monitor critical parameters of unmanned aerial vehicles. Various phenomena characterized by flow-induced vibrations are discussed, including limit cycle oscillations of plates and wing sections, vortex-induced and galloping oscillations of bluff bodies, vortex-induced vibrations of downstream structures, and atmospheric turbulence and gusts. It was found that linear or linearized modeling approaches are commonly employed to support the design phase of energy harvesters. As a result, highly nonlinear and coupled phenomena that characterize flow-induced vibrations are neglected in the design process. The Authors encourage a shift in the current design paradigm: considering coupled nonlinear phenomena, and adequate modeling tools to support their analysis, from a design limitation to a design opportunity. Special emphasis is placed on identifying designs and implementations applicable to aircraft configurations. Application fields of flow-induced vibrations-based energy harvesters are discussed including power supply for wireless sensor networks and simultaneous energy harvest and control. A large body of work on energy harvesters is included in this review journal. Whereas most of the references claim direct applications to unmanned aerial vehicles, it is apparent that, in most of the cases presented, the working principles and characteristics of the energy harvesters are incompatible with any aerospace applications. Finally, the challenges that hold back the integration of energy harvesting

In this paper, a nonlinear wideband multi-mode piezoelectric vibration-based energy harvester (PVEH) is proposed based on a compliant orthoplanar spring (COPS), which has an advantage of providing multiple vibration modes at relatively low frequencies. The PVEH is made of a tri-leg COPS flexible structure, where three fixed-guided beams are capable of generating strong nonlinear oscillations under certain base excitation. A prototype harvester was fabricated and investigated through both finite-element analysis and experiments. The frequency response shows multiple resonance which corresponds to a hardening type of nonlinear resonance. By adding masses at different locations on the COPS structure, the first three vibration modes are brought close to each other, where the three hardening nonlinear resonances provide a wide bandwidth for the PVEH. The proposed PVEH has enhanced performance of the energy harvester in terms of a wide frequency bandwidth and a high-voltage output under base excitations.

This article presents 3-degree-of-freedom theoretical modeling and analysis of a low-frequency vibrationenergy harvester based on diamagnetic levitation. In recent years, although much attention has been placed on vibrationenergy harvesting technologies, few harvesters still can operate efficiently at extremely low frequencies in spite of large potential demand in the field of structural health monitoring and wearable applications. As one of the earliest works, Liu, Yuan and Palagummi proposed vertical and horizontal diamagnetic levitation systems as vibrationenergy harvesters with low resonant frequencies. This study aims to pursue further improvement along this direction, in terms of expanding maximum amplitude and enhancing the flexibility of the operation direction for broader application fields by introducing a new topology of the levitation system.

Vibrationalenergy flow in ferric cytochrome c has been examined by picosecond time-resolved anti-Stokes ultraviolet resonance Raman (UVRR) measurements. By taking advantage of the extremely short nonradiative excited state lifetime of heme in the protein (energy of 20000-25000 cm(-1) was optically deposited selectively at the heme site. Subsequent energy relaxation in the protein moiety was investigated by monitoring the anti-Stokes UVRR intensities of the Trp59 residue, which is a single tryptophan residue involved in the protein that is located close to the heme group. It was found from temporal changes of the anti-Stokes UVRR intensities that the energy flow from the heme to Trp59 and the energy release from Trp59 took place with the time constants of 1-3 and ~8 ps, respectively. These data are consistent with the time constants for the vibrational relaxation of the heme and heating of water reported for hemeproteins. The kinetics of the energy flow were not affected by the amount of excess energy deposited at the heme group. These results demonstrate that the present technique is a powerful tool for studying the vibrationalenergy flow in proteins.

The principal objective of this article is to categorically review and compare the state of the art vibration based energy harvesting approaches. To evaluate the contemporary methodologies with respect to their physics, average power output and operational frequencies, systematically divided and easy readable tables are presented followed by the description of the energy harvesting methods. Energy harvesting is the process of obtaining electrical energy from the surrounding vibratory mechanical systems through an energy conversion method using smart structures, like, piezoelectric, electrostatic materials. Recent advancements in low power electronic gadgets, micro electro mechanical systems, and wireless sensors have significantly increased local power demand. In order to circumvent the energy demand; to allow limitless power supply, and to avoid chemical waste from conventional batteries, low power local energy harvesters are proposed for harvesting energy from different ambient energy sources. Piezoelectric materials have received tremendous interest in energy harvesting technology due to its unique ability to capitalize the ambient vibrations to generate electric potential. Their crystalline configuration allows the material to convert mechanical strain energy into electrical potential, and vice versa. This article discusses the various approaches in vibration based energy scavenging where piezoelectric materials are employed as the energy conversion medium.

We present a MEMS-based unimorph silicon/PZT thick film vibrationalenergy harvester with an integrated proof mass. We have developed a process that allows fabrication of high performance silicon based energy harvesters with a yield higher than 90%. The process comprises a KOH etch using a mechan......We present a MEMS-based unimorph silicon/PZT thick film vibrationalenergy harvester with an integrated proof mass. We have developed a process that allows fabrication of high performance silicon based energy harvesters with a yield higher than 90%. The process comprises a KOH etch using...... a mechanical front side protection of an SOI wafer with screen printed PZT thick film. The fabricated harvester device produces 14.0 μW with an optimal resistive load of 100 kΩ from 1g (g=9.81 m s-2) input acceleration at its resonant frequency of 235 Hz....

Structure-Borne Sound"" is a thorough introduction to structuralvibrations with emphasis on audio frequencies and the associated radiation of sound. The book presents in-depth discussions of fundamental principles and basic problems, in order to enable the reader to understand and solve his own problems. It includes chapters dealing with measurement and generation of vibrations and sound, various types of structural wave motion, structural damping and its effects, impedances and vibration responses of the important types of structures, as well as with attenuation of vibrations, and sound radi

Most of the studies addressed to computations of hydrogen parameters in semiconductor systems, such as silicon, are performed at zero temperature T = 0 K and do not account for contribution of vibrational zero point energy (ZPE). For light weight atoms such as hydrogen (H), however, magnitude of this parameter might be not negligible. This Letter is devoted to clarify the importance of accounting the zero-point vibrations when analyzing hydrogen behavior in silicon and its effect on silicon electronic properties. For this, we estimate the ZPE for different locations and charge states of H in Si. We show that the main contribution to the ZPE is coming from vibrations along the Si-H bonds whereas contributions from other Si atoms apart from the direct Si-H bonds play no role. It is demonstrated that accounting the ZPE reduces the hydrogen formation energy by ˜0.17 eV meaning that neglecting ZPE at low temperatures one can underestimate hydrogen solubility by few orders of magnitude. In contrast, the effect of the ZPE on the ionization energy of H in Si is negligible. The results can have important implications for characterization of vibrational properties of Si by inelastic neutron scattering, as well as for theoretical estimations of H concentration in Si.

Vapor phase fluorescence spectra are used to determine the absolute rate constants for the collisional transfer of vibrationalenergy from initial single vibronic levels of S 1 benzene into the surrounding S 1 vibronic field. 11 initial levels are probed with vibrationalenergies ranging to 2368 cm -1 where the level density is about 10 per cm -1 . CO, isopentane, and S 0 benzene are the collision partners. Benzene rate constants are three to four times gas kinetic for all levels, and electronic energy switching between the initial S 1 molecule and the S 0 collision partner probably makes important contributions. Isopentane efficiencies range from one to two times gas kinetic. Most of the transfer from low S 1 levels occurs with excitation of vibrationalenergy within isopentane. These V--V contributions decline to only about 10% for the high transfer. CO-induced transfer is by V-T,R processes for all levels. The CO efficiency rises from about 0.1 for low regions to about unity for levels above 1500 cm -1 . The CO efficiencies retain significant sensitivity to initial level identity even in the higher regions. Propensity rules derived from collisional mode-to-mode transfer among lower levels of S 1 benzene are used to calculate the relative CO efficiencies. The calculated efficiencies agree well enough with the data to suggest that it may be meaningful to model vibrational equilibration with the use of propensity rules. The rules suggest that only a small number of levels among the thousands surrounding a high initial level contribute significantly to the total relaxation cross section and that this number is rather independent of the level density

The nuclear collective motion is discussed in terms of the Interacting Boson Model (IBM). Results of phenomenological studies by the IBM are presented, and the relation between the IBM and the geometrical models such as the vibration model, the rotor model, etc., is pointed out. A microscopic picture for the IBM is shown, in which bosons are introduced as a tool to describe the motion of nucleon pairs. It is emphasized that the IBM can give a unified understanding of the nuclear collective motion. (author)

Due to the difficulties of obtaining construction site for new plants, following ones are inevitably being built in the site adjacent to existing power plants. Therefore considerable thought has been recently given to the dynamic loading generated by blasting works near the plants to maintain the safety of structures and facilities in power plants. Our own standard for safety level of blast vibration is not prepared yet, and foreign standards have been generally employed without theoretical and experimental verification. Safety-related structures of power plants and facilities have to be protected against the effects of possible hazards due to blast vibration. Earthquakes have been considered a major dynamic design loading as a requirement of plant design, but the effects of blast-induced vibration are not. In order to ensure the safety, rational safe criterion should be established and blast design should be satisfy it, which requires the development of a model for prediction of vibration level through more systematic measurement and analysis. The main objectives of the study are : to provide background data for establishing the rational safe vibration limits, to develop models for prediction of blast vibration level, to establish safe blast design criterion, and to accumulate techniques for field measurements, data acquisition and analysis (author). 80 refs., 347 figs.

This work presents a vulnerability assessment procedure for a complex structure using vibration characteristics. The structural behavior of a three-dimensional framed structure subjected to impact forces was predicted using the spectral element method. The Timoshenko beam function was applied to simulate the impact wave propagations induced by a high-velocity projectile at relatively high frequencies. The interactions at the joints were analyzed for both flexural and longitudinal wave propagations. Simulations of the impact energy transfer through the entire structure were performed using the transient displacement and acceleration responses obtained from the frequency analysis. The kill probabilities of the crucial components for an operating system were calculated as a function of the predicted acceleration amplitudes according to the acceptable vibration levels. Following the proposed vulnerability assessment procedure, the vulnerable positions of a three-dimensional combat vehicle with high possibilities of damage generation of components by impact loading were identified from the estimated vibration responses

Many important chemical and biochemical processes in the condensed phase are notoriously difficult to simulate numerically. Often, this difficulty arises from the complexity of simulating dynamics resulting from coupling to structured, mesoscopic baths, for which no separation of time scales exists and statistical treatments fail. A prime example of such a process is vibrationally assisted charge or energy transfer. A quantum simulator, capable of implementing a realistic model of the system of interest, could provide insight into these processes in regimes where numerical treatments fail. We take a first step towards modeling such transfer processes using an ion-trap quantum simulator. By implementing a minimal model, we observe vibrationally assisted energy transport between the electronic states of a donor and an acceptor ion augmented by coupling the donor ion to its vibration. We tune our simulator into several parameter regimes and, in particular, investigate the transfer dynamics in the nonperturbative regime often found in biochemical situations.

Full Text Available The article discusses a key problem of ship propulsion system vibration diagnostics, which concerns assessing this part of mechanical energy transmitted from the main engine to the ship propeller which is dissipated due to propeller shaft vibration. A simplified calculation model is proposed which allows the total energy of the generated torsional vibration to be assessed from the shaft deflection amplitude measured at the mind-span point between the supports. To verify the developed model, pilot tests were performed on the laboratory rotational mechanical system test rig. In those tests, cyclic bending moment was applied to a unified (cylindrical material sample, which modelled, at an appropriate scale, structural and functional properties of a real propeller shaft.

Advanced maintenance strategies for infrastructure assets such as bridges or off shore wind turbines require actual and reliable information of the maintenance status. Structural health monitoring based on vibration sensing can help in supplying the input needed for structural health monitoring

The problems of flow-induced vibrations of circular cylindrical structures are reviewed. First, the general method of analysis and classification of structural responses are presented. Then, the presentation is broken up along the lines with stationary fluid, parallel flow, and cross flow. Finally, design considerations and future research needs are pointed out. 234 references

A detailed study is carried out of the accuracy of molecular equilibrium geometries obtained from least-squares fits involving experimental rotational constants B(0) and sums of ab initio vibration-rotation interaction constants alpha(r)(B). The vibration-rotation interaction constants have been...... calculated for 18 single-configuration dominated molecules containing hydrogen and first-row atoms at various standard levels of ab initio theory. Comparisons with the experimental data and tests for the internal consistency of the calculations show that the equilibrium structures generated using Hartree......-Fock vibration-rotation interaction constants have an accuracy similar to that obtained by a direct minimization of the CCSD(T) energy. The most accurate vibration-rotation interaction constants are those calculated at the CCSD(T)/cc-pVQZ level. The equilibrium bond distances determined from these interaction...

Full Text Available Self-excited vibration of a square cylinder has been considered as an effective way in harvesting piezoelectric wind energy. In present work, both of the vortex-induced vibration and unstable galloping phenomenon process are investigated in a reduced velocity (Ur=U/ωn·D range of 4≤Ur≤20 with load resistance ranging in 100 Ω≤R≤1 MΩ. The vortex-induced vibration covers presynchronization, synchronization, and postsynchronization branches. An aeroelectromechanical model is given to describe the coupling of the dynamic equation of the fluid-structure interaction and the equation of Gauss law. The effects of load resistance are investigated in both the open-circuit and close-circuit system by a linear analysis, which covers the parameters of the transverse displacement, aerodynamic force, output voltage, and harvested power utilized to measure the efficiency of the system. The highest level of the transverse displacement and the maximum value of harvested power of synchronization branch during the vortex-induced vibration and galloping are obtained. The results show that the large-amplitude galloping at high wind speeds can generate energy. Additionally, energy can be harvested by utilization of the lock-in phenomenon of vortex-induced vibration under low wind speed.

of the coupling coefficient in the feed back control law resulting from the PZT nonlinearity. A minimum energy control law was developed...these control laws we also discovered that the high voltages commanded by our control laws result in the piezoelectric coupling coefficient being...non constant. Thus we also had to implement an adaptive control law (exponential actually) to account for the change in coupling coefficient as the

included early dedicated portable signal averaging equipment, Nomad, CT4 and F18 fatigue test control systems and some field trials. Currently he is...and repairs to acoustically- fatigued structures. ____________________ ________________________________________________ UNCLASSIFIED...Physicists at the Tokyo Institute of Technology investigated various piezoceramic materials [20], developing lead zirconate titanate ( PZT ) in around 1952

developed, based on the theory of radiation filters for estimating the sound radiation from multimodal vibrations. This model has then been used in simulations of optimal feedback control, with special emphasis of the stability margins of the optimal control scheme. Two different methods of designing...... optimal and robust discrete-time feedback controllers for active vibration control of multimodal structures have been compared. They have been showed to yield controllers with identical frequency response characteristics, even though they employ completely different methods of numerical solutions...... and result in different representations of the controllers. The Internal Model Control structure combined with optimal filtering is suggested as an alternative to state space optimal control techniques for designing robust optimal controllers for audio frequency vibration control of resonant structures....

Electronic, structural, vibrational and elastic properties of PaN have been studied both at ambient and high pressures, using first principles methods with several commonly used parameterizations of the exchange-correlation energy. The generalized gradient approximation (GGA) reproduces the groun...

Piezoelectric transducers can be used to harvest electrical energy from structuralvibrations in order to power continuously operating condition monitoring systems local to where they operate. However, excessive vibrations can compromise the safe operation of mechanical systems. Therefore, absorbers are commonly used to control vibrations. With an integrated device, the mechanical energy that otherwise would be dissipated can be converted via piezoelectric transducers. Vibration absorbers are designed to have high damping factors. Hence, the integration of transducers would lead to a low energy conversion. Efficient energy harvesters usually have low damping capabilities; therefore, they are not effective for vibration suppression. Thus, the design of an integrated device needs to consider the two conflicting requirements on the damping. This study focuses on the development of a laboratory test rig with a host structure and a vibration absorber with tunable damping via an active relative velocity feedback. A voice coil actuator is used for this purpose. To overcome the passive damping effects of the back electromagnetic force a novel voltage feedback control is proposed, which has been validated both in simulation and experimentally. The aim of this study is to have a test rig ready for the introduction of piezo-transducers and available for future experimental evaluations of the damping effect on the effectiveness of vibration reduction and energy harvesting efficiency. (paper)

Piezoelectric transducers can be used to harvest electrical energy from structuralvibrations in order to power continuously operating condition monitoring systems local to where they operate. However, excessive vibrations can compromise the safe operation of mechanical systems. Therefore, absorbers are commonly used to control vibrations. With an integrated device, the mechanical energy that otherwise would be dissipated can be converted via piezoelectric transducers. Vibration absorbers are designed to have high damping factors. Hence, the integration of transducers would lead to a low energy conversion. Efficient energy harvesters usually have low damping capabilities; therefore, they are not effective for vibration suppression. Thus, the design of an integrated device needs to consider the two conflicting requirements on the damping. This study focuses on the development of a laboratory test rig with a host structure and a vibration absorber with tunable damping via an active relative velocity feedback. A voice coil actuator is used for this purpose. To overcome the passive damping effects of the back electromagnetic force a novel voltage feedback control is proposed, which has been validated both in simulation and experimentally. The aim of this study is to have a test rig ready for the introduction of piezo-transducers and available for future experimental evaluations of the damping effect on the effectiveness of vibration reduction and energy harvesting efficiency.

Full Text Available INTRODUCTION AND OBJECTIVE: the aim of this study was to investigate whether the addition of vibration during interval training would raise oxygen consumption VO2 to the extent necessary for weight management and to evaluate the influence of the intensity of the vibratory stimulus for prescribing the exercise program in question. METHODS: VO2, measured breath by breath, was evaluated at rest and during the four experimental conditions to determine energy expenditure, metabolic equivalent MET, respiratory exchange ratio RER, % Kcal from fat, and rate of fat oxidation. Eight young sedentary females age 22±1 years, height 163.88± 7.62 cm, body mass 58.35±10.96 kg, and VO2 max 32.75±3.55 mLO2.Kg-1.min-1 performed interval training duration = 13.3 min to the upper and lower limbs both with vibration 35 Hz and 2 mm, 40 Hz and 2 mm, 45 Hz and 2 mm and without vibration. The experimental conditions were randomized and balanced at an interval of 48 hours. RESULTS: the addition of vibration to exercise at 45 Hz and 2 mm resulted in an additional increase of 17.77±12.38% of VO2 compared with exercise without vibration. However, this increase did not change the fat oxidation rate p=0.42 because intensity of exercise 29.1±3.3 %VO2max, 2.7 MET was classified as mild to young subjects. CONCLUSION: despite the influence of vibration on VO2 during exercise, the increase was insufficient to reduce body weight and did not reach the minimum recommendation of exercise prescription for weight management for the studied population.

Two new nine-dimensional potential energy surfaces (PESs) have been generated using high-level ab initio theory for the two main isotopologues of methyl chloride, CH 3 35 Cl and CH 3 37 Cl. The respective PESs, CBS-35 HL , and CBS-37 HL , are based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set (CBS) limit, and incorporate a range of higher-level (HL) additive energy corrections to account for core-valence electron correlation, higher-order coupled cluster terms, scalar relativistic effects, and diagonal Born-Oppenheimer corrections. Variational calculations of the vibrationalenergy levels were performed using the computer program TROVE, whose functionality has been extended to handle molecules of the form XY 3 Z. Fully converged energies were obtained by means of a complete vibrational basis set extrapolation. The CBS-35 HL and CBS-37 HL PESs reproduce the fundamental term values with root-mean-square errors of 0.75 and 1.00 cm −1 , respectively. An analysis of the combined effect of the HL corrections and CBS extrapolation on the vibrational wavenumbers indicates that both are needed to compute accurate theoretical results for methyl chloride. We believe that it would be extremely challenging to go beyond the accuracy currently achieved for CH 3 Cl without empirical refinement of the respective PESs

Two new nine-dimensional potential energy surfaces (PESs) have been generated using high-level ab initio theory for the two main isotopologues of methyl chloride, CH{sub 3}{sup 35}Cl and CH{sub 3}{sup 37}Cl. The respective PESs, CBS-35{sup HL}, and CBS-37{sup HL}, are based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set (CBS) limit, and incorporate a range of higher-level (HL) additive energy corrections to account for core-valence electron correlation, higher-order coupled cluster terms, scalar relativistic effects, and diagonal Born-Oppenheimer corrections. Variational calculations of the vibrationalenergy levels were performed using the computer program TROVE, whose functionality has been extended to handle molecules of the form XY {sub 3}Z. Fully converged energies were obtained by means of a complete vibrational basis set extrapolation. The CBS-35{sup HL} and CBS-37{sup HL} PESs reproduce the fundamental term values with root-mean-square errors of 0.75 and 1.00 cm{sup −1}, respectively. An analysis of the combined effect of the HL corrections and CBS extrapolation on the vibrational wavenumbers indicates that both are needed to compute accurate theoretical results for methyl chloride. We believe that it would be extremely challenging to go beyond the accuracy currently achieved for CH{sub 3}Cl without empirical refinement of the respective PESs.

This work has demonstrated a novel piezoelectric energy harvester without a complex structure and appended component that is capable of scavenging vibrationenergy from arbitrary directions with multiple resonant frequencies. In this harvester, a spiral-shaped elastic thin beam instead of a traditional thin cantilever beam was adopted to absorb external vibration with arbitrary direction in three-dimensional (3D) spaces owing to its ability to bend flexibly and stretch along arbitrary direction. Furthermore, multiple modes in the elastic thin beam contribute to a possibility to widen the working bandwidth with multiple resonant frequencies. The experimental results show that the harvester was capable of scavenging the vibrationenergy in 3D arbitrary directions; they also exhibited triple power peaks at about 16 Hz, 21 Hz, and 28 Hz with the powers of 330 μW, 313 μW, and 6 μW, respectively. In addition, human walking and water wave energies were successfully converted into electricity, proving that our harvester was practical to scavenge the time-variant or multi-directional vibrationenergies in our daily life.

This work has demonstrated a novel piezoelectric energy harvester without a complex structure and appended component that is capable of scavenging vibrationenergy from arbitrary directions with multiple resonant frequencies. In this harvester, a spiral-shaped elastic thin beam instead of a traditional thin cantilever beam was adopted to absorb external vibration with arbitrary direction in three-dimensional (3D) spaces owing to its ability to bend flexibly and stretch along arbitrary direction. Furthermore, multiple modes in the elastic thin beam contribute to a possibility to widen the working bandwidth with multiple resonant frequencies. The experimental results show that the harvester was capable of scavenging the vibrationenergy in 3D arbitrary directions; they also exhibited triple power peaks at about 16 Hz, 21 Hz, and 28 Hz with the powers of 330 μW, 313 μW, and 6 μW, respectively. In addition, human walking and water wave energies were successfully converted into electricity, proving that our harvester was practical to scavenge the time-variant or multi-directional vibrationenergies in our daily life

This work has demonstrated a novel piezoelectric energy harvester without a complex structure and appended component that is capable of scavenging vibrationenergy from arbitrary directions with multiple resonant frequencies. In this harvester, a spiral-shaped elastic thin beam instead of a traditional thin cantilever beam was adopted to absorb external vibration with arbitrary direction in three-dimensional (3D) spaces owing to its ability to bend flexibly and stretch along arbitrary direction. Furthermore, multiple modes in the elastic thin beam contribute to a possibility to widen the working bandwidth with multiple resonant frequencies. The experimental results show that the harvester was capable of scavenging the vibrationenergy in 3D arbitrary directions; they also exhibited triple power peaks at about 16 Hz, 21 Hz, and 28 Hz with the powers of 330 μW, 313 μW, and 6 μW, respectively. In addition, human walking and water wave energies were successfully converted into electricity, proving that our harvester was practical to scavenge the time-variant or multi-directional vibrationenergies in our daily life.

Full Text Available While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibrationenergy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibrationenergy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm3, which was designed for a target frequency of as low as 100 Hz.

While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibrationenergy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibrationenergy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm{sup 3}, which was designed for a target frequency of as low as 100 Hz.

This work has demonstrated a novel piezoelectric energy harvester without a complex structure and appended component that is capable of scavenging vibrationenergy from arbitrary directions with multiple resonant frequencies. In this harvester, a spiral-shaped elastic thin beam instead of a traditional thin cantilever beam was adopted to absorb external vibration with arbitrary direction in three-dimensional (3D) spaces owing to its ability to bend flexibly and stretch along arbitrary direction. Furthermore, multiple modes in the elastic thin beam contribute to a possibility to widen the working bandwidth with multiple resonant frequencies. The experimental results show that the harvester was capable of scavenging the vibrationenergy in 3D arbitrary directions; they also exhibited triple power peaks at about 16 Hz, 21 Hz, and 28 Hz with the powers of 330 μW, 313 μW, and 6 μW, respectively. In addition, human walking and water wave energies were successfully converted into electricity, proving that our harvester was practical to scavenge the time-variant or multi-directional vibrationenergies in our daily life.

The structure-dependent vibrational properties of different Mg(BH4)2 polymorphs (..alpha.., ..beta.., ..gamma.., and ..delta.. phases) were investigated with a combination of neutron vibrational spectroscopy (NVS) measurements and density functional theory (DFT) calculations, with emphasis placed on the effects of the local structure and orientation of the BH4- anions. DFT simulations closely match the neutron vibrational spectra. The main bands in the low-energy region (20-80 meV) are associated with the BH4- librational modes. The features in the intermediate energy region (80-120 meV) are attributed to overtones and combination bands arising from the lower-energy modes. The features in the high-energy region (120-200 meV) correspond to the BH4- symmetric and asymmetric bending vibrations, of which four peaks located at 140, 142, 160, and 172 meV are especially intense. There are noticeable intensity distribution variations in the vibrational bands for different polymorphs. This is explained by the differences in the spatial distribution of BH4- anions within various structures. An example of the possible identification of products after the hydrogenation of MgB2, using NVS measurements, is presented. These results provide fundamental insights of benefit to researchers currently studying these promising hydrogen-storage materials.

A novel multi-frequency energy harvester has been designed and fabricated, which consists of three permanent magnets, three sets of two-layer copper coils and a supported beam of acrylic, while these coils are made of thin fire resistant 4 (FR4) substrates using a standard printed circuit board. The energy under the first, second and third resonant modes can be harvested, corresponding to the resonant frequencies of 369 Hz, 938 Hz and 1184 Hz, respectively. The maximum output voltage and power of the first and second vibration modes are 1.38 mV, 0.6 µW and 3.2 mV, 3.2 µW for a 14 µm exciting vibration amplitude and a 0.4 mm gap between the magnet and coils, respectively. The feasibility study results are in good agreement with the theoretical calculations and show promising application potentials

The maximum output power of energy harvesters driven by harmonic vibrations is well known for a range of specific harvester architectures. An architecture-independent bound based on the mechanical input-power also exists and gives a strict limit on achievable power with one mechanical degree of freedom, but is a least upper bound only for lossless devices. We report a new theoretical bound on the output power of vibrationenergy harvesters that includes parasitic, linear mechanical damping while still being architecture independent. This bound greatly improves the previous bound at moderate force amplitudes and is compared to the performance of established harvester architectures which are shown to agree with it in limiting cases. The bound is a hard limit on achievable power with one mechanical degree of freedom and can not be circumvented by transducer or power-electronic-interface design

This book studies methods for a robust design of rotors against self-excited vibrations. The occurrence of self-excited vibrations in engineering applications if often unwanted and in many cases difficult to model. Thinking of complex systems such as machines with many components and mechanical contacts, it is important to have guidelines for design so that the functionality is robust against small imperfections. This book discusses the question on how to design a structure such that unwanted self-excited vibrations do not occur. It shows theoretically and practically that the old design rule to avoid multiple eigenvalues points toward the right direction and have optimized structures accordingly. This extends results for the well-known flutter problem in which equations of motion with constant coefficients occur to the case of a linear conservative system with arbitrary time periodic perturbations.

Geometry and vibrationalstructure of dibenzo[ b, i][1,4,8,11]tetraaza[14]annulene (TAA) have been studied using infrared and Raman spectroscopy combined with quantum-chemical calculations. The assignments were proposed for 106 out of the total of 108 TAA vibrations, based on comparison of the theoretical predictions with the experimental data obtained for the parent molecule and its isotopomer in which the NH protons were replaced by deuterons. Reassignments were suggesteded for the NH stretching and out-of-plane vibrations. The values of the parameters of the intramolecular NH&ctdot;N hydrogen bonds were analysed in comparison with the corresponding data for porphyrin and porphycene, molecules with the same structural motif, a cavity composed of four nitrogen atoms and two inner protons. Both experiment and calculations suggest that the molecule of TAA is not planar and is present in a trans tautomeric form, with the protons located on the opposite nitrogen atoms.

Over the syears, the rapid growth in railway infrastructure has led to numerous environmental challenges. One such significant issue, particularly in urban areas, is ground-borne vibration. A common source of ground-borne vibration is caused by local defects (e.g. rail joints, switches, turnouts, etc.) that generate large amplitude excitations at isolated locations. Modelling these excitation sources is particularly challenging and requires the use of complex and extensive computational efforts. For some situations, the use of experiments and measured data offers a rapid way to estimate the effect of such defects and to evaluate the railway vibration levels using a scoping approach. In this paper, the problem of railway-induced ground vibrations is presented along with experimental studies to assess the ground vibration and ground borne noise levels, with a particular focus on the structural response of sensitive buildings. The behaviour of particular building foundations is evaluated through experimental data collected in Brussels Region, by presenting the expected frequency responses for various types of buildings, taking into account both the soil-structure interaction and the tramway track response. A second study is dedicated to the Athens metro, where transmissibility functions are used to analyse the effect of various Athenian building face to metro network trough comprehensive measurement campaigns. This allows the verification of appropriate vibration mitigation measures. These benchmark applications based on experimental results have been proved to be efficient to treat a complex problem encountered in practice in urban areas, where the urban rail network interacts with important local defects and where the rise of railway ground vibration problems has clearly been identified.

The simplicity associated with the piezoelectric micro-generators makes it very attractive for MEMS applications, especially for remote systems. In this paper we reviewed the work carried out by researchers during the last three years. The improvements in experimental results obtained in the vibration-based MEMS piezoelectric energy harvesters show very good scope for MEMS piezoelectric harvesters in the field of power MEMS in the near future. (author)

Since 1979, Ford Motor Company has been developing holographic interferometry to supplement more conventional test methods to measure vehicle component vibrations. An Apollo PHK-1 Double Pulse Holographic Laser System was employed to visualize a variety of complex vibration modes, primarily on current production and prototype powertrain components. Design improvements to reduce powertrain response to problem excitations have been deter-mined through pulsed laser holography, and have, in several cases, been put into production in Ford vehicles. Whole-field definition of vibration related deflections provide continuity of information missed by accelerometer/modal analysis techniaues. Certain opera-tional problems, common among pulsed ruby holographic lasers, have reauired ongoing hardware and electronics improvements to minimize system downtime. Real-time, time-averaged and stroboscopic C. W. laser holographic techniques are being developed at Ford to complement the double pulse capabilities and provide rapid identification of modal frequencies and nodal lines for analysis of powertrain structures. Methods for mounting and exciting powertrains to minimize rigid body motions are discussed. Work at Ford will continue toward development of C. W. holographic techniques to provide refined test methodology dedicated to noise and vibration diagnostics with particular emphasis on semi-automated methods for quantifying displacement and relative phase using high resolution digitized video and computers. Continued use of refined pulsed and CW laser holographic interferometry for the analysis of complex structurevibrations seems assured.

This text is an introduction to the dynamics of active structures and to the feedback control of lightly damped flexible structures. The emphasis is placed on basic issues and simple control strategies that work.

Full Text Available Our work aims to find a general solution for the vibrationalenergy flow through a plane network of beams on the basis of an energy flow analysis. A joint between two semi-infinite beams are modeled by three sets of springs and dashpots. Thus, the results can incorporate the case of complaint and non-conservative in all the three degrees of freedom. In the cases of finite coupled structures connected at a certain angle, the derived non-conservative joints and developed wave energy equation were applied. The joint properties, the frequency, the coupling angle, and the internal loss factor were changed to evaluate the proposed methods for predicting medium-to-high frequency vibrationalenergy and intensity distributions.

A discrete velocity method is developed for gas mixtures of diatomic molecules with both rotational and vibrationalenergy states. A full quantized model is described, and rotation-translation and vibration-translation energy exchanges are simulated using a Larsen-Borgnakke exchange model. Elastic and inelastic molecular interactions are modeled during every simulated collision to help produce smooth internal energy distributions. The method is verified by comparing simulations of homogeneous relaxation by our discrete velocity method to numerical solutions of the Jeans and Landau-Teller equations, and to direct simulation Monte Carlo. We compute the structure of a 1D shock using this method, and determine how the rotational energy distribution varies with spatial location in the shock and with position in velocity space.

Health Monitoring of civil structures can be performed by detecting changes in the modal parameters of a structure, or more directly in the measured vibration signals. For a continuous monitoring the excitation of a structure is usually ambient, thus unknown and assumed to be noise. Hence, all estimates from the vibration measurements are realizations of random variables with inherent uncertainty due to (unknown) process and measurement noise and finite data length. In this talk, a strategy for quantifying the uncertainties of modal parameter estimates from a subspace-based system identification approach is presented and the importance of uncertainty quantification in monitoring approaches is shown. Furthermore, a damage detection method is presented, which is based on the direct comparison of the measured vibration signals without estimating modal parameters, while taking the statistical uncertainty in the signals correctly into account. The usefulness of both strategies is illustrated on data from a progressive damage action on a prestressed concrete bridge. References E. Carden and P. Fanning. Vibration based condition monitoring: a review. Structural Health Monitoring, 3(4):355-377, 2004. M. Döhler and L. Mevel. Efficient multi-order uncertainty computation for stochastic subspace identification. Mechanical Systems and Signal Processing, 38(2):346-366, 2013. M. Döhler, L. Mevel, and F. Hille. Subspace-based damage detection under changes in the ambient excitation statistics. Mechanical Systems and Signal Processing, 45(1):207-224, 2014.

In designing large civil engineering structures, an important consideration is prospective dynamic loadings which may include earthquake ground motion, wind gusts, severe sea states and moving vehicles, rotating and reciprocating machinery and others. successful design of such structures requires...... providing for the safety and integrity of the structure, and in some cases also providing for a measure of comfort for the occupants during such loading which the structure and its occupants must endure. Due to these uncertainties, the civil engineering community has traditionally adopted a very...

To properly design and assess a piezoelectric vibrationenergy harvester, it is necessary to consider the application of an efficiency measure of energy conversion. The energy conversion efficiency is defined in this work as the ratio of the electrical output power to the mechanical input power for a piezoelectric vibrationenergy harvester with an impedance-matched load resistor. While previous research works employed the electrical output power for approximate impedance-matched load resistance, this work derives an efficiency measure considering optimally matched resistance. The modified efficiency measure is validated by comparing it with finite element analysis results for piezoelectric vibrationenergy harvesters with three different values of the electro-mechanical coupling coefficient. New findings on the characteristics of energy conversion and conversion efficiency are also provided for the two different impedance matching methods.

The paper deals with analyses and evaluation of vibrationenergy harvesting systems which are based on electromagnetic and piezoelectric physical principles off electro-mechanical conversion. Energy harvesting systems are associated with wireless sensors and a monitoring of engineering objects. The most of engineering objects operate with unwanted mechanical vibrations. However, vibrations could provide an ambient source of energy which is converted into useful electricity. The use of electromagnetic and piezoelectric vibrationenergy harvesters is analyzed in this paper. Thee evaluated output power is used for a choice of the efficient system with respect to the character of vibrations and thee required power output.

The principle of operations of the VEDA program written by the author for Potential Energy Distribution (PED) analysis of theoretical vibrational spectra is described. Nowadays, the PED analysis is indispensible tool in serious analysis of the vibrational spectra. To perform the PED analysis it is necessary to define 3N-6 linearly independent local mode coordinates. Already for 20-atomic molecules it is a difficult task. The VEDA program reads the input data automatically from the Gaussian program output files. Then, VEDA automatically proposes an introductory set of local mode coordinates. Next, the more adequate coordinates are proposed by the program and optimized to obtain maximal elements of each column (internal coordinate) of the PED matrix (the EPM parameter). The possibility for an automatic optimization of PED contributions is a unique feature of the VEDA program absent in any other programs performing PED analysis.

The transfer of vibrationalenergy (V-V) from H 2 to isotopic impurities (HD or D 2 ) has been studied in the liquid state, between 15 and 30 K. The subsequent ralaxation (V-T) of the excited impurity by the H 2 liquid host has also been measured and contrasted with the vibrational relaxation behaviour of pure H 2 and D 2 liquids. The isothermal density dependence of both V-V and V-T transfer has been investigated in the fluid state at 30 K. High density relaxation rates are also compared to the data in the pure gases and to other available gas phase results. Measurements in the solid, near the triple-point temperature, are equally reported for each process studied. (Auth.)

We study various properties of a one-parameter mass term for the Skyrme model, originating from the works of Kopeliovich, Piette and Zakrzewski [V. B. Kopeliovich, B. Piette, and W. J. Zakrzewski, Phys. Rev. D 73, 014006 (2006).], through the use of axially symmetric solutions obtained numerically by simulated-annealing. These solutions allow us to observe asymptotic behaviors of the B=2 binding energies that differ to those previously obtained [B. Piette and W. J. Zakrzewski, Phys. Rev. D 77, 074009 (2008).]. We also decipher the characteristics of three distinct vibrational modes that appear as eigenstates of the vibrational Hamiltonian. This analysis further examine the assertion that the one-parameter mass term offers a better account of baryonic matter than the traditional mass term.

All energy conversion inefficiencies begin with emission of resonant atomic motions, e.g., vibrations, and are declared as waste heat once these motions thermalize to equilibrium. The nonequilibrium energy occupancy of the vibrational modes can be targeted as a harvestable, low entropy energy source for direct conversion to electric energy. Since the lifetime of these resonant vibrations is short, special nanostructures are required with the appropriate tuning of the kinetics. These in turn require multiscale, multiphysics treatments. Atomic vibration is described with quasiparticle phonon in solid, and the optical phonon emission is dominant relaxation channel in semiconductors. These optical modes become over-occupied when their emission rate becomes larger than their decay rate, thus hindering energy relaxation and transport in devices. Effective removal of these phonons by drifting electrons is investigated by manipulating the electron distribution to have higher population in the low-energy states, thus allowing favorable phonon absorption. This is done through introduction, design and analysis of a heterobarrier conducting current, where the band gap is controlled by alloying, thus creating a spatial variation which is abrupt followed by a linear gradient (to ensure directed current). Self-consistent ensemble Monte Carlo simulations based on interaction kinetics between electron and phonon show that up to 19% of the phonon energy is converted to electric potential with an optimized GaAs/AlxGa1-xAs barrier structure over a range of current and electron densities, and this system is also verified through statistical entropy analysis. This direct energy conversion improves the device performance with lower operation temperature and enhances overall energy conversion efficiency. Through this study, the paradigm for harvesting the resonant atomic vibration is proposed, reversing the general role of phonon as only causing electric potential drop. Fundamentals

This paper investigates multi-resonant electromagnetic shunts applied to base isolation for dual-function vibration damping and energy harvesting. Two multi-mode shunt circuit configurations, namely parallel and series, are proposed and optimized based on the H2 criteria. The root-mean-square (RMS) value of the relative displacement between the base and the primary structure is minimized. Practically, this will improve the safety of base-isolated buildings subjected the broad bandwidth ground acceleration. Case studies of a base-isolated building are conducted in both the frequency and time domains to investigate the effectiveness of multi-resonant electromagnetic shunts under recorded earthquake signals. It shows that both multi-mode shunt circuits outperform traditional single mode shunt circuits by suppressing the first and the second vibration modes simultaneously. Moreover, for the same stiffness ratio, the parallel shunt circuit is more effective at harvesting energy and suppressing vibration, and can more robustly handle parameter mistuning than the series shunt circuit. Furthermore, this paper discusses experimental validation of the effectiveness of multi-resonant electromagnetic shunts for vibration damping and energy harvesting on a scaled-down base isolation system.

Excitation coefficients for the production of vibrationally exicted D 2 by low energy electrons have been determined from measurements of the intensity of infrared emission from mixtures of D 2 and small concentrations of CO 2 or CO. The measurements were made using the electron drift tube technique and covered electric field to gas density ratios (E/n) from (5 to 80) x 10 -21 V m 2 , corresponding to mean electron energies between 0.45 and 4.5 eV. The CO 2 and CO concentrations were chosen to allow efficient excitation transfer from the D 2 to the carbon containing molecule, but to minimize direct excitation of the CO 2 or CO. The measured infrared intensities were normalized to predicted values for N 2 --CO 2 and N 2 --CO mixtures at E/n where the efficiency of vibrational excitation is known to be very close to 100%. The experimental excitation coefficients are in satisfactory agreement with predictions based on electron--D 2 cross sections at mean electron energies below 1 eV, but are about 50% too high at mean energies above about 2 eV. Application of the technique to H 2 did not yield useful vibrational excitation coefficients. The effective coefficients in H 2 --CO 2 mixtures were a factor of about 3 times the predicted values. For our H 2 --CO mixtures the excitation of CO via excitation transfer from H 2 is small compared to direct electron excitation of CO molecules. Published experiments and theories on electron--H 2 and electron--D 2 collisions are reviewed to obtain the cross sections used in the predictions

Full Text Available Piezoelectric energy harvesters have proven to have the potential to be a power source in a wide range of applications. As the harvester dimensions scale down, the resonance frequencies of these devices increase drastically. Proof masses are essential in micro-scale devices in order to decrease the resonance frequency and increase the strain along the beam to increase the output power. In this work, the effects of proof mass geometry on piezoelectric energy harvesters are studied. Different geometrical dimension ratios have significant impact on the resonance frequency, e.g., beam to mass lengths, and beam to mass widths. A piezoelectric energy harvester has been fabricated and tested operating at a frequency of about 4 kHz within the audible range. The responses of various prototypes were studied, and an optimized T-shaped piezoelectric vibrationenergy harvester design is presented for improved performance.

Full Text Available A vibration control method based on energy migration is proposed to decrease vibration response of the flexible arm undergoing rigid motion. A type of vibration absorber is suggested and gives rise to the inertial coupling between the modes of the flexible arm and the absorber. By analyzing 1 : 2 internal resonance, it is proved that the internal resonance can be successfully created and the exchange of vibrationenergy is existent. Due to the inertial coupling, the damping enhancement effect is revealed. Via the inertial coupling, vibrationenergy of the flexible arm can be dissipated by not only the damping of the vibration absorber but also its own enhanced damping, thereby effectively decreasing vibration. Through numerical simulations and analyses, it is proven that this method is feasible in controlling nonlinear vibration of the flexible arm undergoing rigid motion.

Wireless sensor networks (WSNs) are nowadays widely used in monitoring and tracking applications. This paper presents the feasibility of using WSNs in active vibration control strategies. The method employed here involves active-structural acoustic control using piezoelectric sensors distributed on a car structure. This system aims at being merged with a WSN whose head node collects data and processes control laws so as to command piezoelectric actuators wisely placed on the structure. We will study the feasibility of implementing WSNs in active vibration control and introduce a complete design methodology to optimize hardware/software and control law synergy in mechatronic systems. A design space exploration will be conducted so as to identify the best WSN platform and the resulting impact on control. (paper)

Vibration-based methods are being rapidly developed and applied to detect structural damage in civil, mechanical and aerospace engineering communities in the last two decades. But uncertainties existing in the structural model and measured vibration data might lead to unreliable results. This paper will present some recent research results to tackle the above mentioned uncertainty problems. By assuming each of the FE model parameters and measured vibration data as a normally distributed random variable, a probabilistic damage detection procedure is developed based on perturbation method and validated by Monte Carlo simulation technique. With this technique, the damage probability of each structural element can be determined. The method developed has been verified by applying it to identify the damages of laboratory tested structures. It was proven that, as compared to the deterministic damage identification method, the present method can not only reduce the possibility of false identification, but also give the identification results in terms of probability. which is deemed more realistic and practical in detecting possible damages in a structure. It has also been found that the modal data included in damage identification analysis have a great influence on the identification results. With a sensitivity study, an optimal measurement set for damage detection is determined. This set includes the optimal measurement locations and the most appropriate modes that should be used in the damage identification analysis. Numerical results indicated that if the optimal set determined in a pre-analysis is used in the damage detection better results will be achieved. (author)

This book is a collection of papers presented at Acoustics and Vibration of Mechanical Structures 2017 – AVMS 2017 – highlighting the current trends and state-of-the-art developments in the field. It covers a broad range of topics, such as noise and vibration control, noise and vibration generation and propagation, the effects of noise and vibration, condition monitoring and vibration testing, modeling, prediction and simulation of noise and vibration, environmental and occupational noise and vibration, noise and vibration attenuators, as well as biomechanics and bioacoustics. The book also presents analytical, numerical and experimental techniques for evaluating linear and non-linear noise and vibration problems (including strong nonlinearity). It is primarily intended for academics, researchers and professionals, as well as PhD students in various fields of the acoustics and vibration of mechanical structures.

Vibrational spectra and molecular structure of anhydrous caffeine have been systematically investigated by second order Moller-Plesset (MP2) perturbation theory and density functional theory (DFT) calculations. Vibrational assignments have been made and many previous ambiguous assignments in IR and Raman spectra are amended. The calculated DFT frequencies and intensities at B3LYP/6-311++G(2d,2p) level, were found to be in better agreement with the experimental values. It was found that DFT with B3LYP functional predicts harmonic vibrational wave numbers more close to experimentally observed value when it was performed on MP2 optimized geometry rather than DFT geometry. The calculated TD-DFT vertical excitation electronic energies of the valence excited states of anhydrous caffeine are found to be in consonance to the experimental absorption peaks.

Energy need from off-grid locations has been critical for effective real-time monitoring and control to ensure structural safety and reliability. To harvest energy from ambient environments, the piezoelectric-based energy-harvesting system has been proven very efficient to convert high frequency vibrations into usable electrical energy. However, due to the low frequency nature of the vibrations of civil infrastructures, such as those induced from vehicle impacts, wind, and waves, the application of a traditional piezoelectric-based energy-harvesting system is greatly restrained since the output power drops dramatically with the reduction of vibration frequencies. This paper focuses on the coupled analysis of a proposed piezoelectric multi-impact wind-energy-harvesting device that can effectively up-convert low frequency wind-induced vibrations into high frequency ones. The device consists of an H-shape beam and four bimorph piezoelectric cantilever beams. The H-shape beam, which can be easily triggered to vibrate at a low wind speed, is originated from the first Tacoma Narrows Bridge, which failed at wind speeds of 18.8 m s-1 in 1940. The multi-impact mechanism between the H-shape beam and the bimorph piezoelectric cantilever beams is incorporated to improve the harvesting performance at lower frequencies. During the multi-impact process, a series of sequential impacts between the H-shape beam and the cantilever beams can trigger high frequency vibrations of the cantilever beams and result in high output power with a considerably high efficiency. In the coupled analysis, the coupled structural, aerodynamic, and electrical equations are solved to obtain the dynamic response and the power output of the proposed harvesting device. A parametric study for several parameters in the coupled analysis framework is carried out including the external resistance, wind speed, and the configuration of the H-shape beam. The average harvested power for the piezoelectric cantilever

This paper presents a homogeneity analysis of a high yield wafer scale fabrication of MEMS-based unimorph silicon/PZT thick film vibrationenergy harvesters aimed towards vibration sources with peak vibrations in the range of around 300Hz. A wafer with a yield of 91% (41/45 devices) has been...

Single rovibrational states of HCl(v=2), HBr(v=2), DCl(v=2), and CO(v=2) were excited with a pulsed optical parametric oscillator (OPO). Total vibrational relaxation rates near - resonance quenchers were measured at 295 0 K using time resolved infrared fluorescence. These rates are attributed primarily to V - V energy transfer, and they generally conform to a simple energy gap law. A small deviation was found for the CO(v) + DCl(v') relaxation rates. Upper limits for the self relaxation by V - R,T of HCl(v=2) and HBr(v=2) and for the two quantum exchange between HCl and HBr were determined. The HF dimer was detected at 295 0 K and 30 torr HF pressure with an optoacoustic spectrometer using the OPO. Pulsed and chopped, resonant and non-resonant spectrophones are analyzed in detail. From experiments and first order perturbation theory, these V - V exchange rates appear to behave as a first order perturbation in the vibrational coordinates. The rotational dynamics are known to be complicated however, and the coupled rotational - vibrational dynamics were investigated theoreticaly in infinite order by the Dillon and Stephenson and the first Magnus approximations. Large ΔJ transitions appear to be important, but these calculations differ by orders of magnitude on specific rovibrational transition rates. Integration of the time dependent semiclassical equations by a modified Gordon method and a rotationally distorted wave approximation are discussed as methods which would treat the rotational motion more accurately. 225 references

Current commercial wireless tire pressure monitoring systems (TPMS) require a battery as electrical power source. The battery limits the lifetime of the TPMS. This limit can be circumvented by replacing the battery by a vibrationenergy harvester. Autonomous wireless TPMS powered by MEMS electret based vibrationenergy harvester have been demonstrated. A remaining technical challenge to attain the grade of commercial product with these autonomous TPMS is the mechanical reliability of the MEMS harvester. It should survive the harsh conditions imposed by the tire environment, particularly in terms of mechanical shocks. As shown in this article, our first generation of harvesters has a shock resilience of 400 g, which is far from being sufficient for the targeted application. In order to improve this aspect, several types of shock absorbing structures are investigated. With the best proposed solution, the shock resilience of the harvesters is brought above 2500 g

Devices with periodic magnetic structures such as wigglers and undulators are often key elements in synchrotron radiation sources. In applications where the coherence of the emitted radiation is important, magnetic field errors distorting the periodicity of the field can significantly reduce the performance of the devices. Thus, the measurement, localization, and correction of the field errors can be a critical issue. This article presents a new method for magnetic field measurements in periodic magnetic structures. The method uses a vibrating taut wire passing through the magnetic structure, and it involves measurements of the amplitudes and phases of the standing waves excited on the wire by the Lorentz force between an AC current in the wire and the surrounding magnetic field. For certain arrangements of the wire, vibrations in the wire will be excited by only non-periodic magnetic field component, i.e., by the error field. By measuring the phase and amplitude of these waves, one can reconstruct the error field distribution and then correct it. The method was tested on a permanent magnet wiggler with 19.8 cm period and a peak field of ∼7000G. It demonstrated ∼0.6G RMS sensitivity, δB rms /B rms ∼1.2x10 -4 and spatial resolution sufficient to identify poles generating the field error. Good agreement was found between field error measurements obtained with the vibrating wire method and with traditional Hall probe field mapping

We present new ab initio calculations of the HF-HF interaction potential for the case where both molecules are simultaneously displaced from their equilibrium internuclear distance. These and previous ab initio calculations are then fit to a new analytic representation which is designed to be efficient to evaluate and to provide an especially faithful account of the forces along the vibrational coordinates. We use the new potential for two sets of quantal scattering calculations for collisions in three dimensions with total angular momentum zero. First we test that the angular harmonic representation of the anisotropy is adequate by comparing quantal rigid rotator calculations to those carried out for potentials involving higher angular harmonics and for which the expansion in angular harmonics is systematically increased to convergence. Then we carry out large-scale quantal calculations of vibration-vibrationenergy transfer including the coupling of both sets of vibrational and rotational coordinates. These calculations indicate that significant rotational energy transfer accompanies the vibration-to-vibrationenergy transfer process.

A unified approach is used to study vibrational properties of periodic systems with first-principles methods and including anharmonic effects. Our approach provides a theoretical basis for the determination of phonon-dependent quantities at finite temperatures. The low-energy portion of the Born-Oppenheimer energy surface is mapped and used to calculate the total vibrationalenergy including anharmonic effects, electron-phonon coupling, and the vibrational contribution to the stress tensor. W...

Full Text Available Inspired by vortex induced vibrationenergy harvesting development as a new source of renewable energy, a T-shaped design vibrationenergy harvester is introduced with the aim of enhancing its performance through vortex induced vibration at near resonance conditions. The T-shaped structural model designed consists of a fixed boundary aluminum bluff splitter body coupled with a cantilever piezoelectric vibrationenergy harvesters (PVEH plate model which is a piezoelectric bimorph plate made of a brass plate sandwiched between 2 lead zirconate titanate (PZT plates. A 3-dimensional Fluid-Structure Interaction simulation analysis is carried out with Reynolds Stress Turbulence Model under wind speed of 7, 10, 12, 14, 16, 18, 19, 20, 22.5, and 25 m/s. The results showed that with 19 m/s wind speed, the model generates 75.758 Hz of vortex frequency near to the structural model’s natural frequency of 76.9 Hz. Resonance lock-in therefore occurred, generating a maximum displacement amplitude of 2.09 mm or a 49.76% increment relatively in vibrational amplitude. Under the effect of resonance at the PVEH plate’s fundamental natural frequency, it is able to generate the largest normalized power of 13.44 mW/cm3g2.

Topological design of miniaturized resonating structures capable of harvesting electrical energy from low frequency environmental mechanical vibrations encounters a particular physical challenge, due to the conflicting design requirements: low resonating frequency and miniaturization. In this paper structural static stiffness to resist undesired lateral deformation is included into the objective function, to prevent the structure from degenerating and forcing the solution to be manufacturable. The rational approximation of material properties interpolation scheme is introduced to deal with the problems of local vibration and instability of the low density area induced by the design dependent body forces. Both density and level set based topology optimization (TO) methods are investigated in their parameterization, sensitivity analysis, and applicability for low frequency energy harvester TO problems. Continuum based variation formulations for sensitivity analysis and the material derivative based shape sensitivity analysis are presented for the density method and the level set method, respectively; and their similarities and differences are highlighted. An external damper is introduced to simulate the energy output of the resonator due to electrical damping and the Rayleigh proportional damping is used for mechanical damping. Optimization results for different scenarios are tested to illustrate the influences of dynamic and static loads. To demonstrate manufacturability, the designs are built to scale using a 3D microfabrication method and assembled into vibrationenergy harvester prototypes. The fabricated devices based on the optimal results from using different TO techniques are tested and compared with the simulation results. The structures obtained by the level set based TO method require less post-processing before fabrication and the structures obtained by the density based TO method have resonating frequency as low as 100 Hz. The electrical voltage response

Periodical control and measurement revealed that vibration level of motor and gearbox which was supported by Cooling Tower Unit 1 at PT Star Energy Geothermal (Wayang Windu) Ltd was significantly increasing since 2013. The vibration was not caused by machinery component failure, but induced by resonance of process flow. Decreasing stiffness of cooling tower structure was suspected causing the increasing vibration level. The physical, chemical, and mechanical properties of wood was deteriorate...

A Fourier-based method is presented to relate changes of the molecular structure during a molecular dynamics simulation with fluctuations in the electronic excitation energy. The method implies sampling of the ground state potential energy surface. Subsequently, the power spectrum of the velocities is compared with the power spectrum of the excitation energy computed using time-dependent density functional theory. Peaks in both spectra are compared, and motions exhibiting a linear or quadratic behavior can be distinguished. The quadratically active motions are mainly responsible for the changes in the excitation energy and hence cause shifts between the dynamic and static values of the spectral property. Moreover, information about the potential energy surface of various excited states can be obtained. The procedure is illustrated with three case studies. The first electronic excitation is explored in detail and dominant vibrational motions responsible for changes in the excitation energy are identified for ethylene, biphenyl, and hexamethylbenzene. The proposed method is also extended to other low-energy excitations. Finally, the vibrational fingerprint of the excitation energy of a more complex molecule, in particular the azo dye ethyl orange in a water environment, is analyzed

Moving inertial loads are applied to structures in civil engineering, robotics, and mechanical engineering. Some fundamental books exist, as well as thousands of research papers. Well known is the book by L. Frýba, Vibrations of Solids and Structures Under Moving Loads, which describes almost all problems concerning non-inertial loads. This book presents broad description of numerical tools successfully applied to structural dynamic analysis. Physically we deal with non-conservative systems. The discrete approach formulated with the use of the classical finite element method results in elemental matrices, which can be directly added to global structure matrices. A more general approach is carried out with the space-time finite element method. In such a case, a trajectory of the moving concentrated parameter in space and time can be simply defined. We consider structures described by pure hyperbolic differential equations such as strings and structures described by hyperbolic-parabolic differential equations ...

A series of forced vibration tests on a full-scale 4-story reinforced concrete test structure was performed to investigate its dynamic response before, after, and during the time it underwent structural damage. Nondestructive tests were conducted first, exciting four translational modes at force levels within the elastic limit, during which the structure suffered no structural damage. Next, a destructive test excited only the lowest translational mode at high-amplitude destructive levels, during which the structure exhibited inelastic response and suffered major structural damage. Post-destructive tests used force levels similar to the nondestructive tests. The work was in support of the program to develop methods for predicting building response to and damage from underground nuclear explosions

A general approach to model vibrational electron energy loss spectra obtained using an electron beam positioned away from the specimen is presented. The energy-loss probability of the fast electron is evaluated using first-principles quantum mechanical calculations (density functional theory) of the dielectric response of the specimen. The validity of the method is assessed using recently measured anhydrous β -guanine, an important molecular solid used by animals to produce structural colors. The good agreement between theory and experiments lays the basis for a quantitative interpretation of this spectroscopy in complex systems.

Vibrationalenergy resulting from intermodal transport systems can be recovered through the use of energy harvesting system consisting of PZT piezo electric material as the primary energy harvesting component. The ability of traditional PZT piezo ele...

The present analysis focuses on vibration transmission within semi-infinite bar structure. The bar is consisting of two different materials in a periodic manner. A periodic bar model is generated using two various methods: The Finite Element method (FEM) and a Floquet theory approach. A parameter...... study is carried out regarding the influence of the number of periods at various frequencies within a semi-infinite bar, stop bands are illustrated at certain periodic intervals within the structure. The computations are carried out in frequency domain in the range below 500 Hz. Results from both...

The paper reports on the combined application of experimental and theoretical methods of vibrational spectroscopy together with low-temperature luminescence data to determine the characteristic features of the formation and structure of complex systems, not only containing ligands directly coordinated to the CA uranium, but also associated with the extraspherical polyatomic electrically charged particles: organic cations. These include uranyl complexes and heterocyclical amines. Studied here were compounds of tetra-halouranylates with pyridine and its derivates, as well as dipyridyl, quinoline and phenanthroline. Structural schemes are also proposed for other uranyl complexes with protonated heterocyclical amines with a more complicated composition, which correctly reflect their spectroscopic properties

A new piezoelectric energy harvester for harnessing energy from flow-induced vibration is developed. It converts flow energy into electrical energy by piezoelectric conversion with oscillation of a piezoelectric film. A finite element model is developed in order to estimate the generated voltage of the piezoelectric laminate subjected to a distributed load. Prototypes of the energy harvester are fabricated and tested. Experimental results show that an open circuit output voltage of 2.2 V pp and an instantaneous output power of 0.2 µW are generated when the excitation pressure oscillates with an amplitude of 1.196 kPa and a frequency of about 26 Hz. The solution of the generated voltage based on the finite element model agrees well with the experiments. Based on the finite element model, the effects of the piezoelectric film dimensions, the fluid pressure applied to the harvester and types of piezoelectric layer on the output voltage of the harvester can be investigated.

This is the fourth workshop on the vibration related to fluid in atomic energy field of Yayoi research group. This time, two topics were taken up. One is edgetone phenomena and the liquid surface vibration phenomena due to flow. Another is the introduction of the experience in light water reactors. The workshop was held on August 30 and 31, 1993 at Nuclear Engineering Research Laboratory, University of Tokyo. At the workshop, lectures were given on the mechanism of occurrence of edgetone, the theoretical analysis of edgetone and edgenoise, the self-excited vibration of free liquid surface due to vertical plane jet and vertical cylindrical jet, the research on flow instability phenomena in parallel loop system, the irregular vibration behavior of U-shaped tubes excited by flow, the research on the vibration of cyclindrical weir due to fluid discharge, the examples of the vibration related to fluid in LWRs, the estimation of fatigue phenomena in bearing rings, the vibration of rotary vanes and verifying test, the analysis of flow in isolated phase bus plate vane and the measurement of velocity distribution, flow in piping and the behavior of valve vibration, the condition for the occurrence of flow vibration in the main steam separation valve of BWR, the vibration of piping due to orifice, the analysis of flow in two-dimensional vibrating cascade, and the subjects of fluid vibration assessment in atomic energy. (K.I.)

Full Text Available Periodical control and measurement revealed that vibration level of motor and gearbox which was supported by Cooling Tower Unit 1 at PT Star Energy Geothermal (Wayang Windu Ltd was significantly increasing since 2013. The vibration was not caused by machinery component failure, but induced by resonance of process flow. Decreasing stiffness of cooling tower structure was suspected causing the increasing vibration level. The physical, chemical, and mechanical properties of wood was deteriorated. The residual strength of the wood had been measured and the data was used to perform dynamic structural analysis on the cooling tower. Several scenarios of structure modification were modelled and drawn, and the best one which the most effectively reducing the vibration level among others was constructed in the field. Triangle inner structure was chosen and applied to modify the cooling tower structure to achieve stiffer and more rigid structure. The vibration level before and after structure modification were measured, and it was proved that the vibration level was significantly reduced after structure modification. Furthermore the cooling tower was not in zone D (danger anymore and the vibration level was accepted according to ISO 10816-3. Keywords: Cooling tower, Dynamic structural analysis, Geothermal power plant, Structural failure, Vibration level

Referring to a container consisting of different shell structures - such as spherical, cylindrical and conical shells - the dynamic behavior of coupled spatial shell structures due to transient loads will be investigated. The spatial structure including the filling of water will be idealized as a three-dimensional model consisting of ring elements. The influence of the water filling on the vibrations will be considered by virtual masses added to the shell structures. In circular direction as well as in meridional direction a consistent mass model has been used. By variation of the virtual masses it will be clarified, how these additional masses influence the vibrational behavior of the composed system. Another aspect which will be investigated is the influence of different stiffnesses of substructures or parts of substructures on the natural frequencies, and on their affiliated eigensystems. Furthermore, the maximum and minimum stresses in the structures caused by transient loads acting on the inner surface of the shells will be explored. Here it seems to be possible to locate an area of maximum strain. Rotational loads as well as nonrotational loads will be considered

Full Text Available For an oscillating system, large amplitude indicates strong vibrationenergy. In this article, modal interaction is used as a useful means to regulate strong nonlinear vibrationenergy of the flexible arm undergoing rigid motion. A method is put forward to migrate and dissipate vibrationenergy based on modal interaction. By means of multiple-scale perturbation analysis, it is proven that internal resonance can be successfully established between modes of the flexible arm and the vibration absorber. Through examples and analyses, it is verified that this control method is effective in regulating strong vibrationenergy and can be used to suppress strong nonlinear vibration of the flexible arm undergoing rigid motion.

Structures of vibrational origin were discovered in vibrationally inelastic electron-CO 2 cross sections in the energy range 0.4-0.9 eV, well below the 2 Π u shape resonance. They appear in the excitation of higher vibrational levels, in particular the highest members of the Fermi polyads of the type (n, 2m, 0) with n+m=2-4. The lowest two structures, at 0.445 and 0.525 eV, are narrow; higher-lying structures are broader and boomerang-like. The structures are absent when the antisymmetric stretch is co-excited. The structures are interpreted in terms of a wavepacket of the nuclei reflected from a potential surface of the CO 2 - anion in a bent and stretched geometry. A state emerging from the virtual state upon bending and stretching and the state resulting from bending the 2 Π u shape resonance are discussed as possibly being responsible for the structures. (author). Letter-to-the-editor

Full Text Available Traditional instrumentation systems used for monitoring vibration of large-scale infrastructure building such as bridges, railway, and others structural building, generally have a complex design. Makes it simple would be very useful both in terms of low-cost and easy maintenance. This paper describes how to develop the instrumentation system. The system is built based on distributed network, with field bus topology, using single-master multi-slave architecture. Master is a control unit, built based on a PC equipped with RS-485 interface. Slave is a sensing unit; each slave was built by integrating a 3-axis vibration sensor with a microcontroller based data acquisition system. Vibration sensor is designed using the main components of a MEMS accelerometer. While the software is developed for two functions: as a control system hardware and data processing. To verify performance of the developed instrumentation system, several laboratory tests have been performed. The result shows that the system has good performance.

An unambiguous assignment of the vibrational spectra of ice I h remains a matter of debate. This study demonstrates that an accurate representation of many-body interactions between water molecules, combined with an explicit treatment of nuclear quantum effects through many-body molecular dynamics (MB-MD), leads to a unified interpretation of the vibrational spectra of ice I h in terms of the structure and dynamics of the underlying hydrogen-bond network. All features of the infrared and Raman spectra in the OH stretching region can be unambiguously assigned by taking into account both the symmetry and the delocalized nature of the lattice vibrations as well as the local electrostatic environment experienced by each water molecule within the crystal. The high level of agreement with experiment raises prospects for predictive MB-MD simulations that, complementing analogous measurements, will provide molecular-level insights into fundamental processes taking place in bulk ice and on ice surfaces under different thermodynamic conditions.

The National Ignition Facility is a laser fusion project that will provide an above-ground experimental capability for nuclear weapons effects simulation. This facility will achieve fusion ignition utilizing solid-state lasers as the energy driver. The facility will cover an estimated 33,400 m 2 at an average height of 5--6 stories. Within this complex, a number of beam transport structures will be houses that will deliver the laser beams to the target area within a 50 microm ms radius of the target center. The beam transport structures are approximately 23 m long and reach approximately heights of 2--3 stories. Low-level ambient random vibrations are one of the primary concerns currently controlling the design of these structures. Low level ambient vibrations, 10 -10 g 2 /Hz over a frequency range of 1 to 200 Hz, are assumed to be present during all facility operations. Each structure described in this paper will be required to achieve and maintain 0.6 microrad ms laser beam pointing stability for a minimum of 2 hours under these vibration levels. To date, finite element (FE) analysis has been performed on a number of the beam transport structures. Certain assumptions have to be made regarding structural uncertainties in the FE models. These uncertainties consist of damping values for concrete and steel, compliance within bolted and welded joints, and assumptions regarding the phase coherence of ground motion components. In this paper, the influence of these structural uncertainties on the predicted pointing stability of the beam line transport structures as determined by random vibration analysis will be discussed

Full Text Available A numerical study is presented, which tailors so-called prestress accumulation-release (PAR strategy to mitigate free vibrations of frame structures. First, the concept of proposed semiactive technique is outlined and possible applications are specified. In the second part of the work a parametric study is discussed, which illustrates the potential of the method for mitigation of free vibrations induced by impact or other initial load scenarios. Special attention is given to the energy balance including all relevant contributions to the total energy of the considered dissipative system. The proposed technique shows a very high potential in mitigation of free vibrations, exceeding 99% of the reference amplitude after 5 cycles of vibration.

The high-rise buildings usually suffer from excessively large wind-induced vibrations, and thus vibration control systems might be necessary. Fluid viscous dampers (FVDs) with nonlinear power law against velocity are widely employed. With the transition of design method from traditional frequency domain approaches to more refined direct time domain approaches, the difficulty of time integration of these systems occurs sometimes. In the present paper, firstly the underlying reason of the difficulty is revealed by identifying that the equations of motion of high-rise buildings installed with FVDs are sometimes stiff differential equations. Thus, an approach effective for stiff differential systems, i.e., the backward difference formula (BDF), is then introduced, and verified to be effective for the equation of motion of wind-induced vibration controlled systems. Comparative studies are performed among some methods, including the Newmark method, KR-alpha method, energy-based linearization method and the statistical linearization method. Based on the above results, a 20-story steel frame structure is taken as a practical example. Particularly, the randomness of structural parameters and of wind loading input is emphasized. The extreme values of the responses are examined, showing the effectiveness of the proposed approach, and also necessitating the refined probabilistic analysis in the design of wind-induced vibration mitigation systems.

Full Text Available Piezoelectric energy harvesting from a vertical geometrically nonlinear cantilever beam with a tip mass subject to transverse harmonic base excitations is analyzed. One piezoelectric patch is placed on the slender beam to convert the tension and compression into electrical voltage. Applying the homotopy analysis method to the coupled electromechanical governing equations, we derive analytical solutions for the horizontal displacement of the tip mass and consequently the output voltage from the piezoelectric patch. Analytical approximation for the frequency response and phase of the geometrically forced nonlinear vibration system are also obtained. The research aims at a rigorous analytical perspective on a nonlinear problem which has previously been solely investigated by numerical and experimental methods.

In order to investigate the relationships between three-dimensional and colinear molecular-collision models with particular emphasis on the role of repulsive and attractive forces in vibrational-energy transfers in gases, a theoretical analysis is developed in this paper. A few known results - mainly the Cottrell and Ream equation, the Takayanagi and the Shin expressions of the transfer probability - relevant to repulsive-force-dominated processes are obtained and/or discussed in the proposed frame. Light is also given on long-range, attractive-forces-dominated processes. The main result of this investigation is that, when a suitable hypothesis is done on the transfer probability, centrifugal effects on the intermolecular trajectories due to standard potentials are negligible in the low-temperature range. A quasi-colinear collision model, which is found to be correlated to the Cottrell and Ream expression for the transfer probability, is regained from a three-dimensional geometry in these conditions. (author)

Full Text Available This paper is about a new manufacturing process aimed at developing stable SiO2/Si3N4 patterned electrets using a Deep Reactive Ion Etching (DRIE step for an application in electret-based VibrationEnergy Harvesters (e-VEH. This process consists in forming continuous layers of SiO2/Si3N4 electrets in order to limit surface conduction phenomena and is a new way to see the problem of electret patterning. Experimental results prove that patterned electrets charged by a positive corona discharge show excellent stability with high surface charge densities that may reach 5mC/m2 on 1.1μm-thick layers, even with fine patterning and harsh temperature conditions (up to 250°C. This paves the way to new e-VEH designs and manufacturing processes.

Full Text Available Gallium arsenide diamondoids structural and vibrational properties are investigated using density functional theory at the PBE/6-31(d level and basis including polarization functions. Variation of energy gap as these diamondoids increase in size is seen to follow confinement theory for diamondoids having nearly equiaxed dimensions. Density of energy states transforms from nearly single levels to band structure as we reach larger diamondoids. Bonds of surface hydrogen with As atoms are relatively localized and shorter than that bonded to Ga atoms. Ga-As bonds have a distribution range of values due to surface reconstruction and effect of bonding to hydrogen atoms. Experimental bulk Ga-As bond length (2.45 Å is within this distribution range. Tetrahedral and dihedral angles approach values of bulk as we go to higher diamondoids. Optical-phonon energy of larger diamondoids stabilizes at 0.037 eV (297 cm-1 compared to experimental 0.035 eV (285.2 cm-1. Ga-As force constant reaches 1.7 mDyne/Å which is comparable to Ga-Ge force constant (1.74 mDyne/Å. Hydrogen related vibrations are nearly constant and serve as a fingerprint of GaAs diamondoids while Ga-As vibrations vary with size of diamondoids.

Formal journal article Experimental analysis of a piezoelectric energy harvesting system for harmonic, random, and sine on random vibration Abstract: Harvesting power with a piezoelectric vibration powered generator using a full-wave rectifier conditioning circuit is experimentally compared for varying sinusoidal, random and sine on random (SOR) input vibration scenarios. Additionally, the implications of source vibration characteristics on harvester design are discussed. Studies in vibration harvesting have yielded numerous alternatives for harvesting electrical energy from vibrations but piezoceramics arose as the most compact, energy dense means of energy transduction. The rise in popularity of harvesting energy from ambient vibrations has made piezoelectric generators commercially available. Much of the available literature focuses on maximizing harvested power through nonlinear processing circuits that require accurate knowledge of generator internal mechanical and electrical characteristics and idealization of the input vibration source, which cannot be assumed in general application. In this manuscript, variations in source vibration and load resistance are explored for a commercially available piezoelectric generator. We characterize the source vibration by its acceleration response for repeatability and transcription to general application. The results agree with numerical and theoretical predictions for in previous literature that load optimal resistance varies with transducer natural frequency and source type, and the findings demonstrate that significant gains are seen with lower tuned transducer natural frequencies for similar source amplitudes. Going beyond idealized steady state sinusoidal and simplified random vibration input, SOR testing allows for more accurate representation of real world ambient vibration. It is shown that characteristic interactions from more complex vibrational sources significantly alter power generation and power processing

Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in

Full Text Available In this work, the main ideas involved in the design of overlapping and multi-overlapping controllers via the Inclusion Principle are discussed and illustrated in the context of the StructuralVibration Control of tall buildings under seismic excitation. A detailed theoretical background on the Inclusion Principle and the design of overlapping controllers is provided. Overlapping and multi-overlapping LQR controllers are designed for a simplified five-story building model. Numerical simulations are conducted to asses the performance of the proposed semi-decentralized controllers with positive results.

Full Text Available Piezoelectret films are prepared by modification of the microstructure of polypropylene foam sheets cross-linked by electronic irradiation (IXPP, followed by proper corona charging. Young’s modulus, relative permittivity, and electromechanical coupling coefficient of the fabricated films, determined by dielectric resonance spectra, are about 0.7 MPa, 1.6, and 0.08, respectively. Dynamic piezoelectric d33 coefficients up to 650 pC/N at 200 Hz are achieved. The figure of merit (FOM, d33 ⋅ g33 for a more typical d33 value of 400 pC/N is about 11.2 GPa−1. Vibration-based energy harvesting with one-layer and two-layer stacks of these films is investigated at various frequencies and load resistances. At an optimum load resistance of 9 MΩ and a resonance frequency of 800 Hz, a maximum output power of 120 μW, referred to the acceleration g due to gravity, is obtained for an energy harvester consisting of a one-layer IXPP film with an area of 3.14 cm2 and a seismic mass of 33.7 g. The output power can be further improved by using two-layer stacks of IXPP films in electric series. IXPP energy harvesters could be used to energize low-power electronic devices, such as wireless sensors and LED lights.

Piezoelectret films are prepared by modification of the microstructure of polypropylene foam sheets cross-linked by electronic irradiation (IXPP), followed by proper corona charging. Young’s modulus, relative permittivity, and electromechanical coupling coefficient of the fabricated films, determined by dielectric resonance spectra, are about 0.7 MPa, 1.6, and 0.08, respectively. Dynamic piezoelectric d{sub 33} coefficients up to 650 pC/N at 200 Hz are achieved. The figure of merit (FOM, d{sub 33} ⋅ g{sub 33}) for a more typical d{sub 33} value of 400 pC/N is about 11.2 GPa{sup −1}. Vibration-based energy harvesting with one-layer and two-layer stacks of these films is investigated at various frequencies and load resistances. At an optimum load resistance of 9 MΩ and a resonance frequency of 800 Hz, a maximum output power of 120 μW, referred to the acceleration g due to gravity, is obtained for an energy harvester consisting of a one-layer IXPP film with an area of 3.14 cm{sup 2} and a seismic mass of 33.7 g. The output power can be further improved by using two-layer stacks of IXPP films in electric series. IXPP energy harvesters could be used to energize low-power electronic devices, such as wireless sensors and LED lights.

Allantoin 2,5-Dioxo-4-imidazolinyl) urea , the diureide of glyoxylic acid, is a crystallisable oxidation product of uric acid found in allantoic and amniotic fluids, in fetal urine and in many plants. It is a healing, moisturizing, soothing and anti-irritating, keratolytic and non-toxic agent useful in dermatological, cosmetic and veterinary preparation. The optimized geometries and energies of the low-energy conformers of allantoin have been calculated using density functional theory (Daft) method. The calculations were performed with Beck's nonlocal three-parameter hybrid functional in combination with the Lee, Yang, and Parr correlation functional (By-play) using the 6-311++G(d,p) basis set. We calculated the infrared frequencies and intensities of the most stable conformers in order to assist in the assignment of the vibrational bands in the experimental spectrum. The B3LYP/6-311+G(d,p) harmonic force constants were scaled by applying the scaled quantum mechanical force field (SQM) technique. The calculated vibrational spectra were interpreted and band assignments were reported

Vortex induced vibration based energy harvesting systems have gained interests in these recent years due to its potential as a low water current energy source. However, the effectiveness of the system is limited only at a certain water current due to the resonance principle that governs the concept. In order to extend the working range, a bistable spring to support the structure is introduced on the system. The improvement on the performance is essentially dependent on the bistable gap as one of the main parameters of the nonlinear spring. A sufficiently large bistable gap will result in a significant performance improvement. Unfortunately, a large bistable gap might also increase a chance of chaotic responses, which in turn will result in diminutive harvested power. To mitigate the problem, an appropriate control structure is required to stabilize the chaotic vibrations of a VIV energy converter with the bistable supporting structure. Based on the nature of the double-well potential energy in a bistable spring, the ideal control structure will attempt to drive the responses to inter-well periodic vibrations in order to maximize the harvested power. In this paper, the OGY control algorithm is designed and implemented to the system. The control strategy is selected since it requires only a small perturbation in a structural parameter to execute the control effort, thus, minimum power is needed to drive the control input. Facilitated by a wake oscillator model, the bistable VIV system is modelled as a 4-dimensional autonomous continuous-time dynamical system. To implement the controller strategy, the system is discretized at a period estimated from the subspace hyperplane intersecting to the chaotic trajectory, whereas the fixed points that correspond to the desired periodic orbits are estimated by the recurrence method. Simultaneously, the Jacobian and sensitivity matrices are estimated by the least square regression method. Based on the defined fixed point and the

EG and G Idaho is assisting the USNRC and the Pressure Vessel Research Committee in supporting a final position on revised damping values for structural analyses of nuclear piping systems. As part of this program, a series of vibrational tests on 76-mm and 203-mm (3-in. amd 8-in.) Schedule 40 carbon steel piping was conducted to determine the changes in structural damping due to various parametric effects. The 10-m (33-ft) straight sections of piping were rigidly supported at the ends. Spring, rod, and constant force hangers, as well as a sway brace and snubbers were included as intermediate supports. Excitation was provided by low-force level hammer inpacts, a hydraulic shaker, and a 445-kN (50-ton) overhead crane. Data was recorded using acceleration, strain, and displacement time histories. This paper presents results from the testing showing the effect of stress level and type of supports on structural damping in piping

This work presents the model of a shear-frame-type structure composed of six flexible beams and three rigid masses. Fixed on the ground, outside the structure, two voltage-controlled electromagnetic actuators are used for vibration control. To model the flexible beams, unidimensional finite...... elements were used. Nonlinear equations for the actuator electromagnetic force, noise in the position sensor, time delays for the control signal update and voltage saturation were also considered in the model. For controlling purposes, a discrete linear quadratic regulator combined with a predictive full......-order discrete linear observer was employed. Results of numerical simulations, where the structure is submitted to an impulsive disturbance force and to a harmonic force, show that the oscillations can be significantly reduced with the use of the electromagnetic actuators....

The propagation of flexural vibration in the periodical membrane-like lattice structure is studied. The band structure calculated with the plane wave expansion method indicates the existence of complete gaps. The frequency response function of a finite periodic structure is simulated with finite element method. Frequency ranges with vibration attenuation are in good agreement with the gaps found in the band structure. Much larger attenuations are found in the complete gaps comparing to those directional ones. The existence of complete flexural vibration gaps in such a lattice structure provides a new idea for vibration control of thin plates

When adopting a vibration controlling structure for a nuclear facility building, it is necessary to evaluate a little longer frequency vibration properly. Although various evaluation methods are proposed, there is no finished method. And, to the earthquake itself to investigate, some factors such as effect of surface wave, distant great earthquake, and so on must be considered, and further various evaluations and investigations are required. Here is reported on an evaluation method of the input earthquake vibration for vibration controlling design establishing on adoption of the vibration controlling structure using a vibration control device comprising of laminated rubber and lead damper for the buildings of reprocessing facility in Tokai Works. The input earthquake vibration for vibration controlling design shown in this report is to be adopted for a vibration controlling facility buildings in the Tokai Works. (G.K.)

Vibrationalenergy levels of the ammonium cation (NH4(+)) and its deuterated isotopomers are calculated using a numerically exact kinetic energy operator on a recently developed nine-dimensional permutation invariant semiglobal potential energy surface fitted to a large number of high-level ab initio points. Like CH4, the vibrational levels of NH4(+) and ND4(+) exhibit a polyad structure, characterized by a collective quantum number P = 2(v1 + v3) + v2 + v4. The low-lying vibrational levels of all isotopomers are assigned and the agreement with available experimental data is better than 1 cm(-1).

Control of Noise and StructuralVibration presents a MATLAB®-based approach to solving the problems of undesirable noise generation and transmission by structures and of undesirable vibration within structures in response to environmental or operational forces. The fundamentals of acoustics, vibration and coupling between vibratingstructures and the sound fields they generate are introduced including a discussion of the finite element method for vibration analysis. Following this, the treatment of sound and vibration control begins, illustrated by example systems such as beams, plates and double plate structures. Sensor and actuator placement is explained as is the idea of modal sensor–actuators. The design of appropriate feedback systems includes consideration of basic stability criteria and robust active structural acoustic control. Single and multi-mode positive position feedback (PPF) control systems are also described in the context of loudspeaker–duct model with non-collocated loudspeaker–microp...

This work presents a novel vibration piezoelectric energy harvester, which is a micro piezoelectric cantilever with multi-beam. The characteristics of the PZT (Pb(Zr{sub 0.53}Ti{sub 0.47})O{sub 3}) thin film were measured; XRD (X-ray diffraction) pattern and AFM (Atomic Force Microscope) image of the PZT thin film were measured, and show that the PZT (Pb(Zr{sub 0.53}Ti{sub 0.47})O{sub 3}) thin film is highly (110) crystal oriented; the leakage current is maintained in nA magnitude, the residual polarisation Pr is 37.037 μC/cm{sup 2}, the coercive field voltage Ec is 27.083 kV/cm, and the piezoelectric constant d{sub 33} is 28 pC/N. In order to test the dynamic performance of the energy harvester, a new measuring system was set up. The maximum output voltage of the single beam of the multi-beam can achieve 80.78 mV under an acceleration of 1 g at 260 Hz of frequency; the maximum output voltage of the single beam of the multi-beam is almost 20 mV at 1400 Hz frequency. .

The molecular structure, vibrational spectra and polarizabilities of Ethyl 4-Dimethylaminobenzoate (EDAB) was investigated by density functional theory employing Becke's three parameter hybrid exchange functional with Lee-Yang-Parr (B3LYP) co-relational functional involving 6-311++G(d,p) basis set and compared with some other levels. A detailed interpretation of the IR and Raman spectra of EDBA have been reported and analyzed. Complete vibrational assignments of the vibrational modes have been done on the basis of the potential energy distribution (TED) using VEDA software. The molecular electrostatic potential mapped onto total density surface has been obtained. A study on the electronic properties, such as absorption wavelength, and frontier molecular orbitals energy, was performed using DFT approach. The stability of the molecule arising from hyper conjugative interactions and accompanying charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The natural and Mulliken charge also calculated and compared with different level of calculation. The dipole moment, polarizability and first, second order hyperpolarizabilities of the title molecule were calculated and compared with the experimental values. The energy gap between frontier orbitals has been used along with electric moments and first order hyperpolarizability, to understand the non linear optical (NLO) activity of the molecule. The NLO activity of molecule was confirmed by SHG analysis.

This paper addresses experimental and theoretical research in fisetin (2-(3,4-dihydroxyphenyl)-3,7-dihydroxychromen-4-one) structure by means of experimental IR and Raman spectroscopies and mechanistic calculations. Density Functional Theory calculations, with M05-2X functional and the 6-311+G (2df, p) basis set implemented in the Gaussian 09 package, are performed with the aim to support molecular structure, vibrational bands' positions and their intensities. Potential energy distribution (PED) values and the description of the largest vibrational contributions to the normal modes are calculated. The most intense bands appear in the 1650-1500 cm -1 wavenumber region. This region involves a combination of the C dbnd O, C2 dbnd C3 and C-C stretching vibrational modes. Most of the bands in the 1500-1000 cm -1 range involve C-C stretching, O-C stretching and in-plane C-C-H, C-O-H, C-C-O and C-C-C bending vibrations of the rings. The region below 1000 cm -1 is characteristic to the combination of in plane C-C-C-H, H-C-C-H, C-C-C-C, C-C-O-C and out of plane O-C-C-C, C-C-O-C, C-C-C-C torsional modes. The Raman spectra of baicalein and quercetin were used for qualitative comparison with fisetin spectrum and verification of band assignments. The applied detailed vibrational spectral analysis and the assignments of the bands, proposed on the basis of fundamentals, reproduced the experimental results with high degree of accuracy.

Vibrationenergy harvesting and sensing is a traditional and growing research field in which various working mechanisms and designs have been developed for an improved performance. Relying on a coupling effect of contact electrification and electrostatic induction, in the past 5 years, triboelectric nanogenerator (TENG) has been applied as a fundamentally new technology to revive the field of vibrationenergy harvesting and self-powered sensing, especially for low-frequency vibrations such as human motion, automobile, machine, and bridge vibrations. The demonstrated instantaneous energy conversion efficiency of ∼70% and a total efficiency up to 85% distinguished TENG from traditional techniques. In this article, both TENG-enabled vibrationenergy harvesting and self-powered active sensing are comprehensively reviewed. Moving toward future development, problems pressing for solutions and onward research directions are also posed to deliver a coherent picture.

Full Text Available Harvesting power with a piezoelectric vibration powered generator using a full-wave rectifier conditioning circuit is experimentally compared for varying sinusoidal, random, and sine on random (SOR input vibration scenarios; the implications of source vibration characteristics on harvester design are discussed. The rise in popularity of harvesting energy from ambient vibrations has made compact, energy dense piezoelectric generators commercially available. Much of the available literature focuses on maximizing harvested power through nonlinear processing circuits that require accurate knowledge of generator internal mechanical and electrical characteristics and idealization of the input vibration source, which cannot be assumed in general application. Variations in source vibration and load resistance are explored for a commercially available piezoelectric generator. The results agree with numerical and theoretical predictions in the previous literature for optimal power harvesting in sinusoidal and flat broadband vibration scenarios. Going beyond idealized steady-state sinusoidal and flat random vibration input, experimental SOR testing allows for more accurate representation of real world ambient vibration. It is shown that characteristic interactions from more complex vibration sources significantly alter power generation and processing requirements by varying harvested power, shifting optimal conditioning impedance, inducing voltage fluctuations, and ultimately rendering idealized sinusoidal and random analyses incorrect.

With the existing trend of minimising material use in typical frame-like civil engineering structures, such as buildings, bridges, and offshore platforms, these structures will typically be subjected to substantial wind induced vibrations. Besides being a source of disturbance for the occupants...

Analyses of the structure and properties of identified pathogenic proteins are important for elucidating the molecular basis of diseases and in drug discovery research. Vibrational spectroscopy has advantages over other techniques in terms of sensitivity of detection of structural changes. Spectral analysis, however, is complicated because the spectrum involves a substantial amount of information. This article includes examples of structural analysis of disease-related proteins using vibrational spectroscopy in combination with additional techniques that facilitate data acquisition and analysis. Residue-specific conformation analysis of an amyloid fibril was conducted using IR absorption spectroscopy in combination with (13)C-isotope labeling, linear dichroism measurement, and analysis of amide I band features. We reveal a pH-dependent property of the interacting segment of an amyloidogenic protein, β2-microglobulin, which causes dialysis-related amyloidosis. We also reveal the molecular mechanisms underlying pH-dependent sugar-binding activity of human galectin-1, which is involved in cell adhesion, using spectroscopic techniques including UV resonance Raman spectroscopy. The decreased activity at acidic pH was attributed to a conformational change in the sugar-binding pocket caused by protonation of His52 (pKa 6.3) and the cation-π interaction between Trp68 and the protonated His44 (pKa 5.7). In addition, we show that the peak positions of the Raman bands of the C4=C5 stretching mode at approximately 1600 cm(-1) and the Nπ-C2-Nτ bending mode at approximately 1405 cm(-1) serve as markers of the His side-chain structure. The Raman signal was enhanced 12 fold using a vertical flow apparatus.

The crystal structure investigations of melamine with phosphorous acid, namely melaminium dihydrogenphosphite monohydrate (C3N6H7·H2PO3·H2O) have been investigated by means of single crystal X-ray diffraction method. The title compound crystallizes in monoclinic crystal system, and the space group is P21/c with a = 10.069 Å, b = 21.592 Å, c = 12.409 Å and Z = 12. The vibrational assignments and analysis of melaminium dihydrogen phosphite monohydrate have also been performed by FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical simulations were performed with DFT (B3LYP) method using 6-31G**, cc-pVTZ, and 6-311++G** basis sets to determine the energy, structural, thermodynamic parameters and vibrational frequencies of melaminium dihydrogen phosphite monohydrate. The hydrogen atom from phosphorous acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak Osbnd H···O and Nsbnd H···O hydrogen bonds shows notable vibrational effects.

Ground vibration from traffic is a source of nuisance in urbanized areas. Trenches and wave barriers can provide mitigation of vibrations, but single barriers need to have a large depth to be effective-especially in the low-frequency range relevant to traffic-induced vibration. Alternatively...

Because of the big inertia and long time constants of energy systems, their long-time behaviour is mainly determined by their present day state and by the trends of their recent evolution. For this reason, it is of prime importance to foresee the evolution of the different energy production sources which may play an important role in the future. A status of the world energy consumption and production is made first using the energy statistics of the IEA. Then, using the trends observed since 1973, the consequences of a simple extrapolation of these trends is examined. Finally, the scenarios of forecasting of energystructures, like those supplied by the International institute for applied systems analysis (IIASA) are discussed. (J.S.)

Full Text Available Due to the presence of system flexibility, impact can excite severe large amplitude vibration responses of the flexible robotic manipulator. This impact vibration exhibits characteristics of remarkable nonlinearity and strong energy. The main goal of this study is to put forward an energy-based control method to absorb and attenuate large amplitude impact vibration of the flexible robotic manipulator. The method takes advantage of internal resonance and is implemented through a vibration absorber based on the transfer and dissipation of energy. The addition of the vibration absorber to the flexible arm generates a coupling effect between vibration modes of the system. By means of analysis on 2:1 internal resonance, the exchange of energy is proven to be existent. The impact vibrationalenergy can be transferred from the arm to the absorber and dissipated through the damping of the absorber. The results of numerical simulations are promising and preliminarily verify that the method is feasible and can be used to combat large amplitude impact vibration of the flexible manipulator undergoing rigid motion.

Energy-harvesting devices collect energy that is being wasted and convert to the electrical energy. For this reason, this type of devices is considered as a convenient alternative to traditional batteries. In this paper, experimental examinations were performed to investigate the application of harvesting device for the reduction of the vibration amplitude in a vibration system and also increase the efficiency of energy-harvesting device. This study focuses on the energy-harvesting device as both producing electrical device and a vibration disabled absorber. In this regard, a motion-based energy-harvesting device is designed to produce electrical energy and also eliminate vibrations of a two joint-end beam which is located under the harmonic excitation force. Then, the governing equations of the forced motion on the main beam are derived and energy-harvesting system are simulated. In addition, the system designed by MATLAB simulation is explained and its results are expressed. Finally, a prototype of the system was made and the ability of the energy-harvesting device to absorb the original system vibrations, as well as parameters impact on the efficiency of energy harvesting is investigated. Experimental results show that the energy-harvesting device, in addition to producing electric current with a maximum value of 1.5V, reduces 94% of the original system vibrations.

In this paper, an energy regenerative seat suspension with a variable external resistance is proposed and built, and a semi-active controller for its vibration control is also designed and validated. The energy regenerative seat suspension is built with a three-phase generator and a gear reducer, which are installed in the scissors structure centre of the seat suspension, and the vibrationenergy is directly harvested from the rotary movement of suspension's scissors structure. The electromagnetic torque of the semi-active seat suspension actuator is controlled by an external variable resistor. An integrated model including the seat suspension's kinematics and the generator is built and proven to match the test result very well. A simplified experimental phenomenon model is also built based on the test results for the controller design. A state feedback H∞ controller is proposed for the regenerative seat suspension's semi-active vibration control. The proposed regenerative seat suspension and its controller are validated with both simulations and experiments. A well-tuned passive seat suspension is applied to evaluate the regenerative seat's performance. Based on ISO 2631-1, the frequency-weighted root mean square (FW-RMS) acceleration of the proposed seat suspension has a 22.84% reduction when compared with the passive one, which indicates the improvement of ride comfort. At the same time, the generated RMS power is 1.21 W. The proposed regenerative seat suspension can greatly improve the driver's ride comfort and has the potential to be developed to a self-powered semi-active system.

We report on the successful extended analysis of the high-frequency (200-700 GHz) part of the gas phase (sub)mm-wave spectra of dimethylsulfoxide (DMSO). The spectrum was recorded at 100 kHz resolution using a solid state subTHz spectrometer. The five lowest energy fundamental vibrational states of DMSO with frequencies below 400 cm-1 were observed as sidebands along with the main 0←0 band. Neglecting the internal rotation of methyls, our rotational Hamiltonian reproduced the spectrum to the subMHz accuracy. We have found that the asymmetric bending state ν23 is the only low frequency fundamental vibrational state with the "anomalous" rotational structure uncovered in Cuisset et al. [1]. dmsomw 2013-09-04 15:03

The phonon spectrum Of C3N4 with defect zincblende-type structure (deltaC(3)N(4)) was calculated by density functional theory (DFT) techniques. The results permit an assessment of important mechanical and thermodynamical properties such as the bulk modulus, lattice specific heat, vibrationenergy,

In this paper, with the aim of providing passive control of structurevibrations a new approach has been proposed for selecting optimal parameters of external electric shunt circuits connected to piezoelectric elements located on the surface of the structure. The approach is based on the mathematical formulation of the natural vibration problem. The results of solution of this problem are the complex eigenfrequencies, the real part of which represents the vibration frequency and the imaginary part corresponds to the damping ratio, characterizing the rate of damping. A criterion of search for optimal parameters of the external passive shunt circuits, which can provide the system with desired dissipative properties, has been derived based on the analysis of responses of the real and imaginary parts of different complex eigenfrequencies to changes in the values of the parameters of the electric circuit. The efficiency of this approach has been verified in the context of natural vibration problem of rigidly clamped plate and semi-cylindrical shell, which is solved for series-connected and parallel -connected external resonance (consisting of resistive and inductive elements) R-L circuits. It has been shown that at lower (more energy-intensive) frequencies, a series-connected external circuit has the advantage of providing lower values of the circuit parameters, which renders it more attractive in terms of practical applications.

Effective development of vibrationenergy harvesters is required to convert ambient kinetic energy into useful electrical energy as power supply for sensors, for example in structural health monitoring applications. Energy harvesting structures exhibiting bistable nonlinearities have previously been shown to generate large alternating current (AC) power when excited so as to undergo snap-through responses between stable equilibria. Yet, most microelectronics in sensors require rectified voltages and hence direct current (DC) power. While researchers have studied DC power generation from bistable energy harvesters subjected to harmonic excitations, there remain important questions as to the promise of such harvester platforms when the excitations are more realistic and include both harmonic and random components. To close this knowledge gap, this research computationally and experimentally studies the DC power delivery from bistable energy harvesters subjected to such realistic excitation combinations as those found in practice. Based on the results, it is found that the ability for bistable energy harvesters to generate peak DC power is significantly reduced by introducing sufficient amount of stochastic excitations into an otherwise harmonic input. On the other hand, the elimination of a low amplitude, coexistent response regime by way of the additive noise promotes power delivery if the device was not originally excited to snap-through. The outcomes of this research indicate the necessity for comprehensive studies about the sensitivities of DC power generation from bistable energy harvester to practical excitation scenarios prior to their optimal deployment in applications.

The structural heterogeneity of water at various interfaces can be revealed by time-resolved sum-frequency generation spectroscopy. The vibrational dynamics of the O–H stretch vibration of interfacial water can reflect structural variations. Specifically, the vibrational lifetime is typically found to increase with increasing frequency of the O–H stretch vibration, which can report on the hydrogen-bonding heterogeneity of water. We compare and contrast vibrational dynamics of water in contact with various surfaces, including vapor, biomolecules, and solid interfaces. The results reveal that variations in the vibrational lifetime with vibrational frequency are very typical, and can frequently be accounted for by the bulk-like heterogeneous response of interfacial water. Specific interfaces exist, however, for which the behavior is less straightforward. These insights into the heterogeneity of interfacial water thus obtained contribute to a better understanding of complex phenomena taking place at aqueous interfaces, such as photocatalytic reactions and protein folding. PMID:29490138

In recent years, the role of molecular vibrations in exciton energy transfer taking place during the first stage of photosynthesis attracted increasing interest. Here, we present a model formulated as a Lindblad-type master equation that enables us to investigate the impact of undamped and especially damped intramolecular vibrational modes on the exciton energy transfer, particularly its efficiency. Our simulations confirm the already reported effects that the presence of an intramolecular vibrational mode can compensate the energy detuning of electronic states, thus promoting the energy transfer; and, moreover, that the damping of such a vibrational mode (in other words, vibrational relaxation) can further enhance the efficiency of the process by generating directionality in the energy flow. As a novel result, we show that this enhancement surpasses the one caused by pure dephasing, and we present its dependence on various system parameters (time constants of the environment-induced relaxation and excitation processes, detuning of the electronic energy levels, frequency of the intramolecular vibrational modes, Huang-Rhys factors, temperature) in dimer model systems. We demonstrate that vibrational-relaxation-enhanced exciton energy transfer (VREEET) is robust against the change of these characteristics of the system and occurs in wide ranges of the investigated parameters. With simulations performed on a heptamer model inspired by the Fenna-Matthews-Olson (FMO) complex, we show that this mechanism can be even more significant in larger systems at T = 300 K. Our results suggests that VREEET might be prevalent in light-harvesting complexes.

Full Text Available The integration of actuators and sensors using smart materials enabled various applications including health monitoring and structuralvibration control. In this study, a robust control technique is designed and implemented in order to reduce vibration of an active structure. Special attention is given to eliminating the possibility of interaction between the health monitoring system and the control system. Exploiting the disturbance decoupling characteristic of the sliding mode observer, it is demonstrated that the proposed observer can eliminate the possible high frequency excitation from the health monitoring system. At the same time, a damage identification scheme, which tracks the changes of mechanical impedance due to the presence of damage, has been applied to assess the health condition of structures. The main objective of this paper is to examine the potential of combining the two emerging techniques together. Using the collocated piezoelectric sensors/actuators for vibration suppression as well as for health monitoring, this technique enabled to reduce the number of system components, while enhancing the performance of structures. As an initial study, both simulation and experimental investigations were performed for an active beam structure. The results show that this integrated technique can provide substantial vibration reductions, while detecting damage on the structure at the same time.

A dynamic model of a coupled rotating drum-disk system with elastic support is developed in this paper. By considering the effects of centrifugal and Coriolis forces as well as rotation-induced hoop stress, the governing differential equation of the drum-disk is derived by Donnell's shell theory. The nonlinear amplitude-frequency characteristics of coupled structure are studied. The results indicate that the natural characteristics of the coupling structure are sensitive to the supporting stiffness of the disk, and the sensitive range is affected by rotating speeds. The circumferential wave numbers can affect the characteristics of the drum-disk structure. If the circumferential wave number n = 1 , the vibration response of the drum keeps a stable value under an unbalanced load of the disk, there is no coupling effect if n ≠ 1 . Under the excitation, the nonlinear hardening characteristics of the forward traveling wave are more evident than that of the backward traveling wave. Moreover, because of the coupling effect of the drum and the disk, the supporting stiffness of the disk has certain effect on the nonlinear characteristics of the forward and backward traveling waves. In addition, small length-radius and thickness-radius ratios have a significant effect on the nonlinear characteristics of the coupled structure, which means nonlinear shell theory should be adopted to design rotating drum's parameter for its specific structural parameters.

This thesis is divided into two major parts. In the first part an experimental study of proton and deuteron transfer in H 2 + + He and HD + + He has been carried out as a function of kinetic and vibrationalenergy. The data gives evidence that at lower kinetic energies, the spectator stripping mechanism indeed plays an important role when H 2 + or HD + is vibrationally excited. The second half of this thesis examines the relative efficiencies between the excitation of C-C stretching vibration and collision energy on the promotion of the H atom transfer reaction of C 2 H 2 + + H 2 → C 2 H 3 + + H

Full Text Available We propose a vibrationenergy harvester consisting of an auxiliary frequency-tuned mass unit and a piezoelectric vibrationenergy harvesting unit for enhancing output power. The proposed integrated system is so configured that its out-of-phase mode can appear at the lowest eigenfrequency unlike in the conventional system using a tuned unit. Such an arrangement makes the resulting system distinctive: enhanced output power at or near the target operating frequency and very little eigenfrequency separation, not observed in conventional eigenfrequency-tuned vibrationenergy harvesters. The power enhancement of the proposed system is theoretically examined with and without tip mass normalization or footprint area normalization.

This research is focused on energy harvesting from track vibration in order to provide power for the wireless sensors which monitor railroad health. Considering that track vibration has vibrationenergy, a new method is proposed in the paper to harvest energy based on the piezoelectric effect. The piezoelectric generator called drum transducer is the key part for track vibrationenergy harvesting. The model of drum transducer is established and the simulation results show that it can generate 100 mW in real track situation. In addition, an experiment rig is developed and its vibration model is also established. The simulation and experiment results show that peak open-circuit voltage of piezoelectric generator is about 50–70 V at the full load of the train. The whole track vibrationenergy harvesting system is analytically modeled, numerically simulated, and experimentally realized to demonstrate the feasibility and the reliability of the theoretical model. This paper is the theoretical basis of harvesting, recovering and recycling of the track vibrationenergy for track safety. (paper)

Practical algorithms for solving realistic inverse problems may often be viewed as problems in nonlinear programming with the data serving as constraints. Such problems are most easily analyzed when it is possible to segment the solution space into regions that are feasible (satisfying all the known constraints) and infeasible (violating some of the constraints). Then, if the feasible set is convex or at least compact, the solution to the problem will normally lie on the boundary of the feasible set. A nonlinear program may seek the solution by systematically exploring the boundary while satisfying progressively more constraints. Examples of inverse problems in wave propagation (traveltime tomography) and vibration (modal analysis) will be presented to illustrate how the variational structure of these problems may be used to create nonlinear programs using implicit variational constraints.

With progress of technology in recent years, gigantism and complication such as high-rise buildings, nuclear reactors and so on have brought about new problems. Particularly, the safety and the reliability for damages in abnormal situations have become more important. Intelligent control systems which can judge whether the situation is normal or abnormal at real time and cope with these situations suitably are demanded. In this study, Cubic Neural Network (CNN) is adopted, which consists of the controllers possessing cubically some levels of information abstracting. In addition to the usual quantitative control, the qualitative control is used for the abnormal situations. And, by selecting a suitable controller, CNN can cope with the abnormal situation. In order to confirm the effectiveness of this system, the structuralvibration control problems with sensory failure and elasto-plastic response are dealt with. As a result of simulations, it was demonstrated that CNN can cope with unexpected abnormal situations which are not considered in learning. (author)

In this paper a resonant control technique, called negative derivative feedback (NDF), for structuralvibration control is presented. Resonant control is a class of control logics, based on the modal approach, which calculates the control action through a dynamic compensator in order to achieve a damping increase on a certain number of system modes. The NDF compensator is designed to work as a band-pass filter, cutting off the control action far from the natural frequencies associated with the controlled modes and reducing the so-called spillover effect. In the paper the proposed control logic is compared both theoretically and experimentally with the most common state-of-the-art resonant control techniques. (paper)

With progress of technology in recent years, gigantism and complication such as high-rise buildings, nuclear reactors and so on have brought about new problems. Particularly, the safety and the reliability for damages in abnormal situations have become more important. Intelligent control systems which can judge whether the situation is normal or abnormal at real time and cope with these situations suitably are demanded. In this study, Cubic Neural Network (CNN) is adopted, which consists of the controllers possessing cubically some levels of information abstracting. In addition to the usual quantitative control, the qualitative control is used for the abnormal situations. And, by selecting a suitable controller, CNN can cope with the abnormal situation. In order to confirm the effectiveness of this system, the structuralvibration control problems with sensory failure and elasto-plastic response are dealt with. As a result of simulations, it was demonstrated that CNN can cope with unexpected abnormal situations which are not considered in learning. (author)

Impulsive energies are abundant throughout the natural and built environments, for instance as stimulated by wind gusts, foot-steps, or vehicle-road interactions. In the interest of maximizing the sustainability of society's technological developments, one idea is to capture these high-amplitude and abrupt energies and convert them into usable electrical power such as for sensors which otherwise rely on less sustainable power supplies. In this spirit, the considerable sensitivity to impulse-type events previously uncovered for bistable oscillators has motivated recent experimental and numerical studies on the power generation performance of bistable vibrationenergy harvesters. To lead to an effective and efficient predictive tool and design guide, this research develops a new analytical approach to estimate the electroelastic response and power generation of a bistable energy harvester when excited by an impulse. Comparison with values determined by direct simulation of the governing equations shows that the analytically predicted net converted energies are very accurate for a wide range of impulse strengths. Extensive experimental investigations are undertaken to validate the analytical approach and it is seen that the predicted estimates of the impulsive energy conversion are in excellent agreement with the measurements, and the detailed structural dynamics are correctly reproduced. As a result, the analytical approach represents a significant leap forward in the understanding of how to effectively leverage bistable structures as energy harvesting devices and introduces new means to elucidate the transient and far-from-equilibrium dynamics of nonlinear systems more generally.

NASA is currently investigating methods to reduce the boil-off rate on large cryogenic upper stages. Two such methods to reduce the total heat load on existing upper stages are vapor cooling of the cryogenic tank support structure and integration of thick multilayer insulation systems to the upper stage of a launch vehicle. Previous efforts have flown a 2-layer MLI blanket and shown an improved thermal performance, and other efforts have ground-tested blankets up to 70 layers thick on tanks with diameters between 2 3 meters. However, thick multilayer insulation installation and testing in both thermal and structural modes has not been completed on a large scale tank. Similarly, multiple vapor cooled shields are common place on science payload helium dewars; however, minimal effort has gone into intercepting heat on large structural surfaces associated with rocket stages. A majority of the vapor cooling effort focuses on metallic cylinders called skirts, which are the most common structural components for launch vehicles. In order to provide test data for comparison with analytical models, a representative test tank is currently being designed to include skirt structural systems with integral vapor cooling. The tank is 4 m in diameter and 6.8 m tall to contain 5000 kg of liquid hydrogen. A multilayer insulation system will be designed to insulate the tank and structure while being installed in a representative manner that can be extended to tanks up to 10 meters in diameter. In order to prove that the insulation system and vapor cooling attachment methods are structurally sound, acoustic testing will also be performed on the system. The test tank with insulation and vapor cooled shield installed will be tested thermally in the B2 test facility at NASAs Plumbrook Station both before and after being vibration tested at Plumbrooks Space Power Facility.

Nowadays broadband vibrationenergy harvesting using piezoelectric effect has become a research hotspot. The innovation in this paper is the widening of the resonant bandwidth of a piezoelectric harvester based on phononic band gaps, which is called one-dimensional phononic piezoelectric cantilever beams (PPCBs). Broadband characteristics of one-dimensional PPCBs are analyzed deeply and the vibration band gap can be calculated. The effects of different parameters on the vibration band gap are presented by both numerical and finite element simulations. Finally experimental tests are conducted to validate the proposed method. It can be concluded that it is feasible to use the PPCB for broadband vibrationenergy harvesting and there should be a compromise among related parameters for low-frequency vibrations.

Chen Zhongsheng, E-mail: czs_study@sina.com [Key Laboratory of Science and Technology on Integrated Logistics Support, College of Mechatronic Engineering and Automation, National University of Defense Technology, Changsha, Hunan 410073 (China); Yang Yongmin; Lu Zhimiao; Luo Yanting [Key Laboratory of Science and Technology on Integrated Logistics Support, College of Mechatronic Engineering and Automation, National University of Defense Technology, Changsha, Hunan 410073 (China)

2013-02-01

Nowadays broadband vibrationenergy harvesting using piezoelectric effect has become a research hotspot. The innovation in this paper is the widening of the resonant bandwidth of a piezoelectric harvester based on phononic band gaps, which is called one-dimensional phononic piezoelectric cantilever beams (PPCBs). Broadband characteristics of one-dimensional PPCBs are analyzed deeply and the vibration band gap can be calculated. The effects of different parameters on the vibration band gap are presented by both numerical and finite element simulations. Finally experimental tests are conducted to validate the proposed method. It can be concluded that it is feasible to use the PPCB for broadband vibrationenergy harvesting and there should be a compromise among related parameters for low-frequency vibrations.

Surface energies of hexagonal and cubic water ice are calculated using first-principles quantum mechanical methods, including an accurate description of anharmonic nuclear vibrations. We consider two proton-orderings of the hexagonal and cubic ice basal surfaces and three proton-orderings of hexagonal ice prism surfaces, finding that vibrations reduce the surface energies by more than 10%. We compare our vibrational densities of states to recent sum frequency generation absorption measurements and identify surface proton-orderings of experimental ice samples and the origins of characteristic absorption peaks. We also calculate zero point quantum vibrational corrections to the surface electronic band gaps, which range from −1.2 eV for the cubic ice basal surface up to −1.4 eV for the hexagonal ice prism surface. The vibrational corrections to the surface band gaps are up to 12% smaller than for bulk ice.

Full Text Available This paper proposes mechanism and control algorithm for pneumatic relaxation system of suspension with vibrationenergy recuperation applied to standard vehicle operator seat (“Sibeko” company. Mathematical model of the seat pneumatic relaxation suspension with two additional air volumes was created. Pneumatic motor – recuperator activated by means of air flow from the one additional volume to another is installed in air piping between additional volumes. Computational research was made in Matlab/Simulink. Amplitude-frequency characteristics of transmission coefficient for standard and proposed suspensions were plotted for preliminary evaluation of vibration protection properties of seat suspension. Performed comparative analysis of amplitude-frequency characteristics shows that noticeable improvement of vibration protection properties of pneumatic relaxation suspension system with vibrationenergy recuperation in comparison with standard system both in region of resonance disturbances and in above-resonance region. Main ways for further improvement of vibration protection properties of proposed system were marked out.

This paper reports the experimental and theoretical study on the structure and vibrations of 2-Methylphenyl boronic acid (2MPBA). The different spectroscopic techniques such as FT-IR (4000-400 cm-1) and FT-Raman (4000-50 cm-1) of the title molecule in the solid phase were recorded. The geometry of the molecule was fully optimized using density functional theory (DFT) (B3LYP) with 6-311++G(d, p) basis set calculations. The vibrational wavenumbers were also corrected with scale factor to take better results for the calculated data. Vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the potential energy distribution (PED) of the vibrational modes obtained from VEDA 4 program. The calculated wavenumbers showed the best agreement with the experimental results. Whereas, it is observed that, the theoretical frequencies are more than the experimental one for O-H stretching vibration modes of the title molecule.

Collective protein modes are expected to be important for facilitating energy transfer in the Fenna-Matthews-Olson (FMO) complex of photosynthetic green sulphur bacteria, however to date little work has focussed on the microscopic details of these vibrations. The nonlinear network model (NNM) provides a computationally inexpensive approach to studying vibrational modes at the microscopic level in large protein structures, whilst incorporating anharmonicity in the inter-residue interactions which can influence protein dynamics. We apply the NNM to the entire trimeric FMO complex and find evidence for the existence of nonlinear discrete breather modes. These modes tend to transfer energy to the highly connected core pigments, potentially opening up alternative excitation energy transfer routes through their influence on pigment properties. Incorporating localised modes based on these discrete breathers in the optical spectra calculations for FMO using ab initio site energies and excitonic couplings can substantially improve their agreement with experimental results.

In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structuralvibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structuralvibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.

Full Text Available In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structuralvibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structuralvibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.

The trend of finding new means to harvest energy has triggered numerous researches to explore the potential of raindrop energy harvesting. This paper presents an investigation on raindrop energy harvesting which compares the performance of polyvinylidene fluoride (PVDF) cantilever and bridge structure transducers and the development of a raindrop energy harvesting system. The parameters which contribute to the output voltage such as droplet size, droplets released at specific heights and dimensions of PVDF transducers are analyzed. Based on the experimental results, the outcomes have shown that the bridge structure transducer generated a higher voltage than the cantilever. Several dimensions have been tested and it was found that the 30 mm × 4 mm × 25 μm bridge structure transducer generated a relatively high AC open-circuit voltage, which is 4.22 V. The power generated by the bridge transducer is 18 μW across a load of 330 kΩ. The transducer is able to drive up a standard alternative current (AC) to direct current (DC) converter (full-wave bridge rectifier). It generated a DC voltage, V DC of 8.7 mV and 229 pW across a 330 kΩ resistor per drop. It is also capable to generate 9.3 nJ in 20 s from an actual rain event.

Extensive vibrational investigations of 2-amino-4-methoxybenzothiazole have been carried out with FTIR and FT-Raman spectral techniques. The electronic structure of the molecule has been analysed by UV-Visible and NMR spectroscopies. The DFT studies were carried out with B3LYP and HF methods utilising 6-31G(d,p), 6-311++G(d,p) and cc-pVDZ basis sets to determine the structural, thermodynamical, vibrational, electronic characteristics of the compound and also to understand the electronic and steric influence of the methoxy amino groups on the skeletal frequencies. The mixing of the fundamental modes was determined with the help of total energy distribution (TED). The energies of the frontier molecular orbitals have also been determined. The kinetic and thermodynamic stability and chemical hardness of the molecule have been determined. Complete NBO analysis was also carried out to find out the intramolecular electronic interactions and their stabilisation energy. 1H and 13C NMR chemical shifts and the electronic transitions of the molecule are also discussed.

Full Text Available The piezoelectric transduction mechanism is a common vibration-to-electric energy harvesting approach. Piezoelectric energy harvesters are typically mounted on a vibrating host structure, whereby alternating voltage output is generated by a dynamic strain field. A design target in this case is to match the natural frequency of the harvester to the ambient excitation frequency for the device to operate in resonance mode, thus significantly increasing vibration amplitudes and, as a result, energy output. Other fundamental vibration modes have strain nodes, where the dynamic strain field changes sign in the direction of the cantilever length. The paper reports on a dimensionless numerical transient analysis of a cantilever of a constant cross-section and an optimally-shaped cantilever with the objective to accurately predict the position of a strain node. Total effective strain produced by both cantilevers segmented at the strain node is calculated via transient analysis and compared to the strain output produced by the cantilevers segmented at strain nodes obtained from modal analysis, demonstrating a 7% increase in energy output. Theoretical results were experimentally verified by using open-circuit voltage values measured for the cantilevers segmented at optimal and suboptimal segmentation lines.

On the basis of experimental and theoretical studies of vibbrational spectra for halides, sulfates, phosphates, uranyl oxalates (and uranium) as well as for more complicated complex systems, reliable spectroscopic criteria have been established for estimation of their structural features by more simple and accessible (than direct) methods. Due to coordination to a central ion of U/sup 6/(U/sup 4/) ligands a geometry variation specific for each method of addition occurs and concomitant redistribution of the force interaction in the mentioned system as well, which directly affects the variation of their frequency characteristics and vibration modes. On this ground stable indications of particular types of coordination for mono- and polyatomic groups (including bridge-type, characteristic of polymetric structures) are pointed out in the IR absorption and Raman spectra. In the investigated structures the predominant effect of coordination on the spectral properties of complexes, as compared with other factors (for example, outer-sphere binding) is established. The presence of water molecules in an interlayer space does not tell essentially on the state of polyatomic ligands with all donor atoms bound with the uranium central atom (particularly, in binary uranyl phosphates). In the presence of free oxygen atoms the H/sub 2/O effect can lead only to some shift of the maxima of separate bands and their additional weak splitting (in uranyl sulfates).

Differential scattering experiments are reported for proton impact on N 2 , CO, and NO in the energy range E/sub lab/=30--80 eV. The measurements include the range of very small scattering angles around 0 0 as well as the rainbow region. The vibrationally resolved energy-loss spectra show a relatively low vibrational inelasticity for all three systems. Differential cross sections, transition probabilities, and the mean vibrationalenergy transfer are presented. Rotational excitation is indicated by the broadening of the energy-loss peaks which is most significant for H + --NO. The small-angle scattering data for vibrational excitation in CO show good agreement with the impact parameter theory using the known long-range interactions for this system

Vibrationenergy harvesting and sensing is a traditional and growing research field in which various working mechanisms and designs have been developed for an improved performance. Relying on a coupling effect of contact electrification

The dynamics of jacket supported offshore wind turbine (OWT) in earthquake environment is one of the progressing focuses in the renewable energy field. Soil-structure interaction (SSI) is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper (MTMD) in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology (RSM) has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions: fixed base (without SSI) and flexible base (with SSI). Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit. Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance.

North Atlantic EnergyStructures Inc. is in the process of designing a tidal fence for a site near the Straits of Belle Isle. This presentation provided details of both the design and the location in which the wave energy plant will be installed. Design constraints included a short seasonal work window, and a harsh but pristine environment. Design specifications of the paddlewheels and caissons were presented. The paddlewheel is iceberg and slab ice resistant, and has portals below the wheel axis, a water-free upper chamber, and bi-directional power generation. The planned installation sequence was presented, as well as details of a hydrodynamic simulation examining torque on the turbines in the tidal energy chamber. Results of the study indicated that 20 paddlewheels per caisson provided the equivalent of 12 MW of energy. A tidal fence of 70 to 80 caissons provided the equivalent of 1.2 GW of energy. A slab ice simulation study was outlined, and details of the pumping station, inlet and hydro-generation station were provided. A map of the proposed siting of the tidal fence was presented. It was concluded that financing for the pilot project has been granted. However, further financing for research and development is required. refs., tabs., figs.

Galfenol traditional cantilever energy harvesters (TCEHs) have bigger electrical output only at resonance and exhibit nonlinear mechanical-magnetic-electric coupled (NMMEC) behaviors. To increase low-frequency broadband performances of a TCEH, an improved CEH (ICEH) with magnetic repulsive force is studied. Based on the magnetic dipole model, the nonlinear model of material, the Faraday law and the dynamic principle, a lumped parameter NMMEC model of the devices is established. Comparisons between the calculated and measured results show that the proposed model can provide reasonable data trends of TCEH under acceleration, bias field and different loads. Simulated results show that ICEH exhibits low-frequency resonant, hard spring and bistable behaviors, thus can harvest more low-frequency broadband vibrationenergy than TCEH, and can elicit snap-through and generate higher voltage even under weak noise. The proposed structure and model are useful for improving performances of the devices.

Full Text Available A conductive direct-write process of multilayered coils for micro electromagnetic generators is proposed. This novel approach of using silver ink to form the conductive structures largely reduces the fabrication complexity, and it provides a faster alternative to the conventional semiconductor methods. Multi-layered coils with insulation were accurately layered on a micromachined cantilevered diaphragm by a dispenser. Coils several layers thick could be used to increase the power output and double coils were separated by a layer of insulation. Six prototypes, all capable of efficient conversion of vibrationalenergy into electrical energy, were fabricated. The experimental results, which include measurements of the electromotive force and power output, are presented. Prototypes with two coils and thicker conducting layers had less resistance and the power output was much more than that of a single-coil unit. This generator can produce 82 nW of power at a resonance frequency of 275 Hz under 5 g excitation.

Creating orderly periodic micro/nano-structures on metallic surfaces, or structural coloration, for control of surface apparent color and optical reflectivity has been an exciting research topic over the years. The direct applications of structural coloration include color marking, display devices, and invisibility cloak. This paper presents an efficient method to colorize metallic surfaces with periodic micro/nano-gratings using elliptical vibration texturing. When the tool vibration is coupled with a constant cutting velocity, controlled periodic ripples can be generated due to the overlapping tool trajectory. These periodic ripples with a wavelength near visible spectrum can act as micro-gratings to introduce iridescent colors. The proposed technique also provides a flexible method for color marking of metallic surfaces with arbitrary patterns and images by precise control of the spacing distance and orientation of induced micro/nano-ripples. Theoretical analysis and experimental results are given to demonstrate structural coloration of metals by a direct mechanical machining technique.

The sensitivity of molecular vibrational population dynamics, governing the CO laser operated in fundamental and overtone transitions, to vibration-to-vibration rate constants is investigated. With this aim, three rate constant sets have been used, differing in their completeness (i.e. accounting for single-quantum exchange only, or for multi-quantum exchange with a limited number of rate constants obtained by semiclassical calculations, and, finally, with an exhaustive set of rate constants including asymmetric exchange processes, as well) and in the employed interaction potential. The most complete set among these three is introduced in this paper. An existing earlier kinetic model was updated to include the latter new data. Comparison of data produced by kinetic modelling with the above mentioned sets of rate constants shows that the vibrational distribution function, and, in particular, the CO overtone laser characteristics, are very sensitive to the choice of the model. The most complete model predicts slower evolution of the vibrational distribution, in qualitative agreement with experiments

Power source is critical to achieve independent and autonomous operations of electronic mobile devices. The vibration-based energy harvesting is extensively studied recently, and recognized as a promising technology to realize inexhaustible power supply for small-scale electronics. Among various approaches, the piezoelectric energy harvesting has gained the most attention due to its high conversion efficiency and simple configurations. However, most of piezoelectric energy harvesters (PEHs) to date are based on bending-beam structures and can only generate limited power with a narrow working bandwidth. The insufficient electric output has greatly impeded their practical applications. In this paper, we present an innovative lead zirconate titanate (PZT) energy harvester, named high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH), to enhance the performance of energy harvesters. A theoretical model was developed analytically, and solved numerically to study the nonlinear characteristics of the HC-PEH. The results estimated by the developed model agree well with the experimental data from the fabricated prototype. The HC-PEH shows strong nonlinear responses, favorable working bandwidth and superior power output. Under a weak excitation of 0.3 g (g = 9.8 m/s2), a maximum power output 30 mW is generated at 22 Hz, which is about ten times better than current energy harvesters. The HC-PEH demonstrates the capability of generating enough power for most of wireless sensors.

Experimental and theoretical vibrational spectra of β-2-aminopyridinium dihydrogenphosphate (β-2APDP) have been investigated. The FT-IR spectrum of β-2APDP was recorded in the region 4000-400 cm -1. The optimized molecular structure and theoretical vibrational frequencies of β-2APDP have been investigated using ab initio Hartree-Fock (HF) and density functional B3LYP method with 6-311++G(d,p) basis set. The optimized geometric parameters (bond lengths and bond angles) and theoretical frequencies have been compared with the corresponding experimental data and it is found that they agree well with each other. All the assignments of the theoretical frequencies were performed by potential energy distributions using VEDA 4 program. Furthermore, the used scale factors were obtained from the ratio of the frequency values of the strongest peaks in the experimental and theoretical IR spectra. From the results it was concluded that the B3LYP method is superior to the HF method for the vibrational frequencies.

Vibrationenergy harvesters can serve as a replacement solution to batteries for powering tire pressure monitoring systems (TPMS). Autonomous wireless TPMS powered by microelectromechanical system (MEMS) electret-based vibrationenergy harvester have been demonstrated. The mechanical reliability of the MEMS harvester still has to be assessed in order to bring the harvester to the requirements of the consumer market. It should survive the mechanical shocks occurring in the tire environment. A testing procedure to quantify the shock resilience of harvesters is described in this article. Our first generation of harvesters has a shock resilience of 400 g, which is far from being sufficient for the targeted application. In order to improve this aspect, the first important aspect is to understand the failure mechanism. Failure is found to occur in the form of fracture of the device’s springs. It results from impacts between the anchors of the springs when the harvester undergoes a shock. The shock resilience of the harvesters can be improved by redirecting these impacts to nonvital parts of the device. With this philosophy in mind, we design three types of shock absorbing structures and test their effect on the shock resilience of our MEMS harvesters. The solution leading to the best results consists of rigid silicon stoppers covered by a layer of Parylene. The shock resilience of the harvesters is brought above 2500 g. Results in the same range are also obtained with flexible silicon bumpers, which are simpler to manufacture. (paper)

Vibrationenergy harvesters can serve as a replacement solution to batteries for powering tire pressure monitoring systems (TPMS). Autonomous wireless TPMS powered by microelectromechanical system (MEMS) electret-based vibrationenergy harvester have been demonstrated. The mechanical reliability of the MEMS harvester still has to be assessed in order to bring the harvester to the requirements of the consumer market. It should survive the mechanical shocks occurring in the tire environment. A testing procedure to quantify the shock resilience of harvesters is described in this article. Our first generation of harvesters has a shock resilience of 400 g, which is far from being sufficient for the targeted application. In order to improve this aspect, the first important aspect is to understand the failure mechanism. Failure is found to occur in the form of fracture of the device’s springs. It results from impacts between the anchors of the springs when the harvester undergoes a shock. The shock resilience of the harvesters can be improved by redirecting these impacts to nonvital parts of the device. With this philosophy in mind, we design three types of shock absorbing structures and test their effect on the shock resilience of our MEMS harvesters. The solution leading to the best results consists of rigid silicon stoppers covered by a layer of Parylene. The shock resilience of the harvesters is brought above 2500 g. Results in the same range are also obtained with flexible silicon bumpers, which are simpler to manufacture.

This paper presents a nonlinear doubly magnet-coupled energy harvesting system (DMEHS) which could exhibit co-bistable and monostable dynamic characteristics. Its various characteristic responses induced by the magnetic force can be conveniently obtained using the adjustable horizontal distance between two coupled harvesters in the DMEHS. In the case of appropriate relative positions, the DMEHS appears in a co-bistable structure which is different from the traditional bistable structure. Additionally, both the inclination angle of endmost magnets and the displacement perpendicular to the vibration direction are taken into account to calculate the nonlinear magnetic force in the nonlinear electromechanical equations. The numerical investigations show good agreement with experimental results with respect to the output voltage response. Each harvester without magnetic coupling is tested independently to compare with the DMEHS. Both numerical and experimental results also demonstrate the frequency bandwidth and performance enhancements by changing the horizontal distance between the two coupled harvesters. (paper)

Turbulent cooling water in the Compact Linear Collider (CLIC) accelerating structures will inevitably induce some vibrations. The maximum acceptable amplitude of vibrations is small, as vibrations in the accelerating structure could lead to beam jitter and alignment difficulties. A Finite Element Analysis model is needed to identify the conditions under which turbulent instabilities and significant vibrations are induced. Due to the orders of magnitude difference between the fluid motion and the structure’s motion, small vibrations of the structure will not contribute to the turbulence of the cooling fluid. Therefore the resonant conditions of the cooling channels presented in this paper, directly identify the natural frequencies of the accelerating structures to be avoided under normal operating conditions. In this paper a 2D model of the cooling channel is presented finding spots of turbulence being formed from a shear layer instability. This effect is observed through direct visualization and wavelet ana...

Understanding the role of water, hydrate and hydroxyl species on nanoparticle surfaces and interfaces is very important in both physical and life sciences. Detecting the presence of oxygen-hydrogen species with nanometer resolution is extremely challenging at present. Here we show that the recently developed vibrational electron energy-loss spectroscopy using subnanometer focused electron beams can be employed to spectroscopically identify the local presence and variation of OH species on nanoscale surfaces. The hydrogen-oxygen fingerprint can be correlated with highly localized structural and morphological information obtained from electron imaging. Moreover, the current approach exploits the aloof beam mode of spectral acquisition which does not require direct electron irradiation of the sample thus greatly reducing beam damage to the OH bond. These findings open the door for using electron microscopy to probe local hydroxyl and hydrate species on nanoscale organic and inorganic structures. - Highlights: • High spatial resolution spectroscopic detection of water related species in nanoparticles. • Detection of OH stretch modes with vibrational EELS. • Differentiation between hydrate and hydroxide species on or on nanoparticles. • Detection of hydrate on a single 60 nm oxide nanoparticle of MgO. • Use of aloof beam EELS to minimize radiation damage.

The Tokai reprocessing facility buildings are constituted by a lower foundation, vibration controlling layers, and upper structure. At the vibration controlling layer, a laminated rubber aiming support of the building load and extension of the eigenfrequency and a damper aiming absorption of earthquake energy are provided. Of course, the facility buildings are directly supported at the arenaceous shale (Taga Layer) of the Miocene in the Neogene confirmed to the stablest ground, as well the buildings with high vibration resistant importance in Japan. This report shows that when the vibration controlling structure is adopted for the reprocessing facility buildings where such high vibration resistance is required, reduction of input acceleration for equipments and pipings can be achieved and the earthquake resistant safety can also be maintained with sufficient tolerance and reliability. (G.K.)

Non-adiabatic vibrational-electronic resonance in the excited electronic states of natural photosynthetic antennas drastically alters the adiabatic framework, in which electronic energy transfer has been conventionally studied, and suggests the possibility of exploiting non-adiabatic dynamics for directed energy transfer. Here, a generalized dimer model incorporates asymmetries between pigments, coupling to the environment, and the doubly excited state relevant for nonlinear spectroscopy. For this generalized dimer model, the vibrational tuning vector that drives energy transfer is derived and connected to decoherence between singly excited states. A correlation vector is connected to decoherence between the ground state and the doubly excited state. Optical decoherence between the ground and singly excited states involves linear combinations of the correlation and tuning vectors. Excitonic coupling modifies the tuning vector. The correlation and tuning vectors are not always orthogonal, and both can be asymmetric under pigment exchange, which affects energy transfer. For equal pigment vibrational frequencies, the nonadiabatic tuning vector becomes an anti-correlated delocalized linear combination of intramolecular vibrations of the two pigments, and the nonadiabatic energy transfer dynamics become separable. With exchange symmetry, the correlation and tuning vectors become delocalized intramolecular vibrations that are symmetric and antisymmetric under pigment exchange. Diabatic criteria for vibrational-excitonic resonance demonstrate that anti-correlated vibrations increase the range and speed of vibronically resonant energy transfer (the Golden Rule rate is a factor of 2 faster). A partial trace analysis shows that vibronic decoherence for a vibrational-excitonic resonance between two excitons is slower than their purely excitonic decoherence.

Vibrationalenergy flow through molecules remains a perennial problem in chemical physics. Usually vibrationalenergy dynamics are viewed through the lens of time-dependent level populations. This is natural because lasers naturally pump and probe vibrational transitions, but it is also useful to think of vibrationalenergy as being conducted from one location in a molecule to another. We have developed a new technique where energy is driven into a specific part of molecules adsorbed on a metal surface, and ultrafast nonlinear coherent vibrational spectroscopy is used to watch the energy arrive at another part. This technique is the analog of a flash thermal conductance apparatus, except it probes energy flow with angstrom spatial and femtosecond temporal resolution. Specific examples to be presented include energy flow along alkane chains, and energy flow into substituted benzenes. Ref: Z. Wang, J. A. Carter, A. Lagutchev, Y. K. Koh, N.-H. Seong, D. G. Cahill, and D. D. Dlott, Ultrafast flash thermal conductance of molecular chains, Science 317, 787-790 (2007). This material is based upon work supported by the National Science Foundation under award DMR 0504038 and the Air Force Office of Scientific Research under award FA9550-06-1-0235.

Vibrational-electronic resonance in photosynthetic pigment-protein complexes invalidates Förster's adiabatic framework for interpreting spectra and energy transfer, thus complicating determination of how the surrounding protein affects pigment properties. This paper considers the combined effects of vibrational-electronic resonance and inhomogeneous variations in the electronic excitation energies of pigments at different sites on absorption, emission, circular dichroism, and hole-burning spectra for a non-degenerate homodimer. The non-degenerate homodimer has identical pigments in different sites that generate differences in electronic energies, with parameters loosely based on bacteriochlorophyll a pigments in the Fenna-Matthews-Olson antenna protein. To explain the intensity borrowing, the excited state vibrational-electronic eigenvectors are discussed in terms of the vibrational basis localized on the individual pigments, as well as the correlated/anti-correlated vibrational basis delocalized over both pigments. Compared to those in the isolated pigment, vibrational satellites for the correlated vibration have the same frequency and precisely a factor of 2 intensity reduction through vibrational delocalization in both absorption and emission. Vibrational satellites for anti-correlated vibrations have their relaxed emission intensity reduced by over a factor 2 through vibrational and excitonic delocalization. In absorption, anti-correlated vibrational satellites borrow excitonic intensity but can be broadened away by the combination of vibronic resonance and site inhomogeneity; in parallel, their vibronically resonant excitonic partners are also broadened away. These considerations are consistent with photosynthetic antenna hole-burning spectra, where sharp vibrational and excitonic satellites are absent. Vibrational-excitonic resonance barely alters the inhomogeneously broadened linear absorption, emission, and circular dichroism spectra from those for a

A first-principles plane wave self-consistent method with the ultra-soft-pseudopotential scheme in the framework of the density functional theory (DFT) is performed to study structural, electronic and vibrational properties of LaP for Rock-salt (NaCl/Bl) and Cesium-chloride (CsCl/B2) phases. The instability of Rock-salt (NaCl/Bl) phases around the transition is discussed. Conclusions based on electronic energy band structure, density of state, phonon dispersion and phonon density of states in both phases are outlined. The calculated results are consistence and confirm the successful applicability of quasi-harmonic phonon theory for structural instability studies for the alloys.

A first-principles plane wave self-consistent method with the ultra-soft-pseudopotential scheme in the framework of the density functional theory (DFT) is performed to study structural, electronic and vibrational properties of LaP for Rock-salt (NaCl/Bl) and Cesium-chloride (CsCl/B2) phases. The instability of Rock-salt (NaCl/Bl) phases around the transition is discussed. Conclusions based on electronic energy band structure, density of state, phonon dispersion and phonon density of states in both phases are outlined. The calculated results are consistence and confirm the successful applicability of quasi-harmonic phonon theory for structural instability studies for the alloys.

A new implementation of vibrational coupled-cluster (VCC) theory is presented, where all amplitude tensors are represented in the canonical polyadic (CP) format. The CP-VCC algorithm solves the non-linear VCC equations without ever constructing the amplitudes or error vectors in full dimension but still formally includes the full parameter space of the VCC[n] model in question resulting in the same vibrationalenergies as the conventional method. In a previous publication, we have described the non-linear-equation solver for CP-VCC calculations. In this work, we discuss the general algorithm for evaluating VCC error vectors in CP format including the rank-reduction methods used during the summation of the many terms in the VCC amplitude equations. Benchmark calculations for studying the computational scaling and memory usage of the CP-VCC algorithm are performed on a set of molecules including thiadiazole and an array of polycyclic aromatic hydrocarbons. The results show that the reduced scaling and memory requirements of the CP-VCC algorithm allows for performing high-order VCC calculations on systems with up to 66 vibrational modes (anthracene), which indeed are not possible using the conventional VCC method. This paves the way for obtaining highly accurate vibrational spectra and properties of larger molecules.

Noise is a nuisance to people, and buildings should therefore be designed to prevent propagation of sound and vibration in the audible frequency range as well as the range of frequencies relevant to whole-body vibrations of humans. In heavy structures made of concrete and masonry, a source...

The objective of this study was to determine if transverse vibration methods could be used to effectively assess the structural integrity of wood floors as component systems. A total of 10 wood floor systems, including 3 laboratory-built floor sections and 7 in-place floors in historic buildings, were tested. A forced vibration method was applied to the floor systems...

Vibration-based energy harvesting using piezoelectric circular diaphragms (PCDs) with a structure featuring the central mass (C-mass) configuration has drawn much attention in recent decades. In this work, we propose a new configuration with the annular proof mass (A-mass) where an improved energy harvesting is promised. The numerical analysis was employed using the circuit-coupled piezoelectric simulation, and the experimental validation was implemented using PCDs with the even-width annular electrodes. Samples with the different mass configurations as well as structural parameters ϖ 1 and ϖ 2, which indicate the ratio between the inner boundary radius and piezoelectric ceramic radius as well as the ratio between outer boundary radius and the substrate radius, respectively, were prepared and tested. The impedance-matched output power of full-electrode PCDs was also collected, and some distinct improvement was measured on samples with the certain structural parameters. The power increases from 14.1 mW to 19.0 mW after changing the configuration from C-mass to A-mass with the same parameters (ϖ 1, ϖ 2) = (0.16, 0.9), showing the considerable improvement in energy harvesting by using A-mass configuration.

Dedicated, self-powered wireless sensors are widely being studied for use throughout many industries to monitor everyday operations, maintain safety, and report performance characteristics. To enable sensors to power themselves, harvesting energy from machine vibration has been studied, however, its overall effectiveness can be hampered due to small vibration amplitudes and thus limited harvestable energy density. This paper addresses the issue by proposing a novel vibrationenergy harvester architecture in which a compliant mechanism and proof mass system is used to amplify the vibrational velocity of machine vibration for a linear electromagnetic generator. A prototype has been fabricated and experimentally characterized to verify its effectiveness. When operating at its natural frequency in a low base amplitude, 0.001 inch (25.4 μm) at 19.4 Hz, during lab tests, the harvester has been shown to produce up to 0.91 V AC open voltage, and a maximum power of 2 mW, amplifying the relative proof mass velocity by approximately 5.4 times. This method of locally increasing the machine vibrational velocity has been shown to be a viable option for increasing the potential power output of an energy harvester. In addition, a mathematical model is created based on pseudo-rigid-body dynamics and the analysis matches closely with experiments.

The role of molecular rotations in the exchange of vibrational and translational energy is investigated for collisions between anharmonic diatomic molecules and structureless atoms. A three-dimensional, semiclassical, impact parameter description is applied with emphasis directed towards the influence of rotational coupling on the net rate of vibrationalenergy transfer summed over all final rotational states. These results are then related to the predictions of an equivalent collinear collision model, and their comparison allows an evaluation of the collinear approximation. The mechanisms of vibrationalenergy transfer including rotational transitions are shown to be separable into three classes, with the molecules belonging to each class identified first and foremost by their ratio of fundamental vibrational and rotational frequencies, ω/sub e//B/sub e/, and second by the proximity of their initial state to a near-resonant vibration--rotation transition with a small change in angular momentum. While the dynamics of molecules with ω/sub e//B/sub e/ ratios that are comparable to the range of angular momentum transitions having strong coupling are found to require a complete three-dimensional description, the rates of vibrationalenergy transfer in molecules with large ω/sub e//B/sub e/ ratios appear to be well approximated by a collinear collision model

Full Text Available Car body design in view of structural performance and lightweighting is a challenging task due to all the performance targets that must be satisfied such as vehicle safety and ride quality. In this paper, material replacement along with multidisciplinary design optimization strategy is proposed to develop a lightweight car body structure that satisfies the crash and vibration criteria while minimizing weight. Through finite element simulations, full frontal, offset frontal, and side crashes of a full car model are evaluated for peak acceleration, intrusion distance, and the internal energy absorbed by the structural parts. In addition, the first three fundamental natural frequencies are combined with the crash metrics to form the design constraints. The wall thicknesses of twenty-two parts are considered as the design variables. Latin Hypercube Sampling is used to sample the design space, while Radial Basis Function methodology is used to develop surrogate models for the selected crash responses at multiple sites as well as the first three fundamental natural frequencies. A nonlinear surrogate-based optimization problem is formulated for mass minimization under crash and vibration constraints. Using Sequential Quadratic Programming, the design optimization problem is solved with the results verified by finite element simulations. The performance of the optimum design with magnesium parts shows significant weight reduction and better performance compared to the baseline design.

For structures subject to impact loads, the residual vibration reduction is more and more important as the machines become faster and lighter. An efficient sensitivity analysis of residual vibration with respect to structural or operational parameters is indispensable for using a gradient based optimization algorithm, which reduces the residual vibration in either active or passive way. In this paper, an integrated quadratic performance index is used as the measure of the residual vibration, since it globally measures the residual vibration response and its calculation can be simplified greatly with Lyapunov equation. Several sensitivity analysis approaches for performance index were developed based on the assumption that the initial excitations of residual vibration were given and independent of structural design. Since the resulting excitations by the impact load often depend on structural design, this paper aims to propose a new efficient sensitivity analysis method for residual vibration of structures subject to impacts to consider the dependence. The new method is developed by combining two existing methods and using adjoint variable approach. Three numerical examples are carried out and demonstrate the accuracy of the proposed method. The numerical results show that the dependence of initial excitations on structural design variables may strongly affects the accuracy of sensitivities.

The modal parameters such as natural frequency and vibration mode of the frame structure of the layer stiffness sensitivity is inconsistent. This article focuses on the theoretical derivation of the frequency and mode of the frame structure layer stiffness of the first-order sensitivity. The numerical examples show that the frame structure of layer stiffness higher than with the first order sensitivity vibration frequency.

Full Text Available Acoustic and vibration control for an underwater structure under mechanical excitation has been investigated by using negative feedback control algorithm. The underwater structure is modeled with cylindrical shells, conical shells, and circular bulkheads, of which the motion equations are built with the variational approach, respectively. Acoustic property is analyzed by the Helmholtz integration formulation with boundary element method. Based on negative feedback control algorithm, a control loop with a coupling use of piezoelectric sensor and actuator is built, and accordingly some numerical examples are carried out on active control of structuralvibration and acoustic response. Effects of geometrical and material parameters on acoustic and vibration properties are investigated and discussed.

We have examined a piezoelectric unimorph cantilever (PUC) with unequal piezoelectric and nonpiezoelectric lengths for vibrationenergy harvesting theoretically by extending the analysis of a PUC with equal piezoelectric and nonpiezoelectric lengths. The theoretical approach was validated by experiments. A case study showed that for a fixed vibration frequency, the maximum open-circuit induced voltage which was important for charge storage for later use occurred with a PUC that had a nonpiezo...

Future deployment of wireless sensor networks will ultimately require a self-sustainable local power source for each sensor, and vibrationenergy harvesting is a promising approach for such applications. A requirement for efficient vibrationenergy harvesting is to match the device and source frequencies. While techniques to tune the resonance frequency of an energy harvesting device have recently been described, in many applications optimization of such systems will require the energy harvesting device to be able to autonomously tune its resonance frequency. In this work a vibrationenergy harvesting device with autonomous resonance frequency tunability utilizing a magnetic stiffness technique is presented. Here a piezoelectric cantilever beam array is employed with magnets attached to the free ends of cantilever beams to enable magnetic force resonance frequency tuning. The device is successfully tuned from − 27% to + 22% of its untuned resonance frequency while outputting a peak power of approximately 1 mW. Since the magnetic force tuning technique is semi-active, energy is only consumed during the tuning process. The developed prototype consumed maximum energies of 3.3 and 3.9 J to tune to the farthest source frequencies with respect to the untuned resonance frequency of the device. The time necessary for this prototype device to harvest the energy expended during its most energy-intensive (largest resonant frequency adjustment) tuning operation is 88 min in a low amplitude 0.1g vibration environment, which could be further optimized using higher efficiency piezoelectric materials and system components

This report discusses the application of modern signal processing techniques to characterize parameters governing the vibrational response of a structure. Simulated response data is used to explore the feasibility of applying these techniques to various structural problems. On-line estimator/indentifiers are used to estimate structural parameters, validate designed structures, and detect structural failure when used with a detector

The influence of mechanical vibration on the flow properties of a highly concentrated multiphase food system is explored in this work. An experimental set-up was designed and adapted to a conventional rotational rheometer with precise rheological characterization capability. A number of calibration tests were performed prior to fundamental experiments with a highly concentrated chocolate suspension. Also, the prediction of wall slippage in shear flow under vibration was evaluated. Analysis of the boundary conditions shows that no side effects such as wall slippage or the Taylor effect were present during the shear experiment under vibration. It was found that superposition of mechanical vibration and shear flow radically decreases the shear viscosity. Comparison between reference shear viscosities at specified shear rates and those measured under vibration shows considerable differences in flow properties. Conversion of the behaviour of the concentrated suspension from strongly shear-thinning to Newtonian flow is reported. Also, the appearance of vibration-induced dilatancy as a new phenomenon is described. It is suggested to relate such phenomena to the non-equilibrium between structure formation and disintegration under vibration and hydrodynamic forces of shear flow. The influence of vibration on structure formation can be well observed during measurement of the yield value of the chocolate suspension under vibration. Comparison with reference data shows how sensitive the structure of the concentrated suspension is to vibration in general. The effects and observations revealed provide a solid basis for further fundamental investigations of structure formation regularities in the flow of any highly concentrated system. The results also show the technological potential for non-conventional treatment of concentrated, multiphase systems.

We report differential cross sections (DCSs) for electron-impact vibrational-excitation of tetrahydrofuran, at intermediate incident electron energies (15-50 eV) and over the 10°-90° scattered electron angular range. These measurements extend the available DCS data for vibrational excitation for this species, which have previously been obtained at lower incident electron energies (≤20 eV). Where possible, our data are compared to the earlier measurements in the overlapping energy ranges. Here, quite good agreement was generally observed where the measurements overlapped.

As an alternative power solution for low-power devices, harvesting energy from the ambient mechanical vibration has received increasing research interest in recent years. In this paper we study the transient dynamic characteristics of a piezoelectric energy harvesting system including a piezoelectric energy harvester, a bridge rectifier, and a storage capacitor. To accomplish this, this energy harvesting system is modeled, and the charging process of the storage capacitor is investigated by employing the in-phase assumption. The results indicate that the charging voltage across the storage capacitor and the gathered power increase gradually as the charging process proceeds, whereas the charging rate slows down over time as the charging voltage approaches to the peak value of the piezoelectric voltage across the piezoelectric materials. In addition, due to the added electrical damping and the change of the system natural frequency when the charging process is initiated, a sudden drop in the vibration amplitude is observed, which in turn affects the charging rate. However, the vibration amplitude begins to increase as the charging process continues, which is caused by the decrease in the electrical damping (i.e., the decrease in the energy removed from the mechanical vibration). This electromechanical coupling characteristic is also revealed by the variation of the vibration amplitude with the charging voltage. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

A combined synthesis, experiment, and theory approach, using elastic and inelastic helium atom scattering along with ab initio density functional perturbation theory, has been used to investigate the vibrational dynamics and band structure of a recently synthesized organic-functionalized semiconductor interface. Specifically, the thermal properties and lattice dynamics of the underlying Ge(111) semiconductor crystal in the presence of a commensurate (1 × 1) methyl adlayer were defined for atomically flat methylated Ge(111) surfaces. The mean-square atomic displacements were evaluated by analysis of the thermal attenuation of the elastic He diffraction intensities using the Debye-Waller model, revealing an interface with hybrid characteristics. The methyl adlayer vibrational modes are coupled with the Ge(111) substrate, resulting in significantly softer in-plane motion relative to rigid motion in the surface normal. Inelastic helium time-of-flight measurements revealed the excitations of the Rayleigh wave across the surface Brillouin zone, and such measurements were in agreement with the dispersion curves that were produced using density functional perturbation theory. The dispersion relations for H-Ge(111) indicated that a deviation in energy and lineshape for the Rayleigh wave was present along the nearest-neighbor direction. The effects of mass loading, as determined by calculations for CD 3 -Ge(111), as well as by force constants, were less significant than the hybridization between the Rayleigh wave and methyl adlayer librations. The presence of mutually similar hybridization effects for CH 3 -Ge(111) and CH 3 -Si(111) surfaces extends the understanding of the relationship between the vibrational dynamics and the band structure of various semiconductor surfaces that have been functionalized with organic overlayers

A combined synthesis, experiment, and theory approach, using elastic and inelastic helium atom scattering along with ab initio density functional perturbation theory, has been used to investigate the vibrational dynamics and band structure of a recently synthesized organic-functionalized semiconductor interface. Specifically, the thermal properties and lattice dynamics of the underlying Ge(111) semiconductor crystal in the presence of a commensurate (1 × 1) methyl adlayer were defined for atomically flat methylated Ge(111) surfaces. The mean-square atomic displacements were evaluated by analysis of the thermal attenuation of the elastic He diffraction intensities using the Debye-Waller model, revealing an interface with hybrid characteristics. The methyl adlayer vibrational modes are coupled with the Ge(111) substrate, resulting in significantly softer in-plane motion relative to rigid motion in the surface normal. Inelastic helium time-of-flight measurements revealed the excitations of the Rayleigh wave across the surface Brillouin zone, and such measurements were in agreement with the dispersion curves that were produced using density functional perturbation theory. The dispersion relations for H-Ge(111) indicated that a deviation in energy and lineshape for the Rayleigh wave was present along the nearest-neighbor direction. The effects of mass loading, as determined by calculations for CD{sub 3}-Ge(111), as well as by force constants, were less significant than the hybridization between the Rayleigh wave and methyl adlayer librations. The presence of mutually similar hybridization effects for CH{sub 3}-Ge(111) and CH{sub 3}-Si(111) surfaces extends the understanding of the relationship between the vibrational dynamics and the band structure of various semiconductor surfaces that have been functionalized with organic overlayers.

We present the results of high level ab initio calculations for the structure, harmonic and anharmonic spectroscopic constants, and ring puckering barrier of cyclobutane (C4H8) in an effort to establish the minimum theoretical requirements needed for their accurate description. We have found that accurate estimates for the barrier between the minimum (D(2d)) and transition state (D(4h)) configurations require both higher levels of electron correlation [MP4, CCSD(T)] and orbital basis sets of quadruple-zeta quality or larger. By performing CCSD(T) calculations with basis sets as large as cc-pV5Z, we were able to obtain, for the first time, a value for the puckering barrier that lies within 10 cm(-1) (or 2%) from experiment, whereas the best previously calculated values were in errors exceeding 40% of experiment. Our best estimate of 498 cm(-1) for the puckering barrier is within 10 cm(-1) of the experimental value proposed originally, but it lies approximately 50 cm(-1) higher than the revisited value, which was obtained more recently using different assumptions regarding the coupling between the various modes. It is therefore suggested that revisiting the analysis of the experimental data might be warranted. Our best computed values (at the CCSD(T)/aug-cc-pVTZ level of theory) for the equilibrium structural parameters of C4H8 are r(C-C) = 1.554 A, r(C-H(alpha)) = 1.093 A, r(C-H(beta)) = 1.091 A, phi(C-C-C) = 88.1 degrees , alpha(H(alpha)-C-H(beta)) = 109.15 degrees , and theta = 29.68 degrees for the puckering angle. We have found that the puckering angle theta is more sensitive to the level of electron correlation than to the size of the basis set for a given method. We furthermore present anharmonic calculations that are based on a second-order perturbative evaluation of rovibrational parameters and their effects on the vibrational spectra and average structure. We have found that the anharmonic calculations predict the experimentally measured fundamental band

In the nuclear structure part, the foundations of Faessler and Greiner's rotation-vibration coupling theory are reviewed, whereafter an alternative derivation of Faessler and Greiner's Hamiltonian is presented. A non-spherical quadrupole phonon number N is defined and used in the matrix elements reported for odd-even/even-odd nuclei. These matrix elements are shown to evince oblate-prolate effects that can be exploited for assessing the signs of quadrupole deformations. In the nuclear reaction part, the wave functions emerging from the structure part are applied in a complete and consistent description of elastic and inelastic particle scattering, one-nucleon transfer, and particle/γ-ray angular correlations. The intentions are to demonstrate that anomolous angular distributions and 1=2 j-effects observed in one-nucleon transfer are interrelated phenomena, that can be satisfactorily explained in terms of the elementary vibrational excitation modes inherent in Faessler and Greiner's theory. The latter is regarded as a non-spherical approach to the theory of the quadrupole component of the nuclear potential energy surface. (Auth.)

This paper describes the characterization of thin-film MEMS vibrationenergy harvesters based on aluminum nitride as piezoelectric material. A record output power of 85 μW is measured. The parasitic-damping and the energy-harvesting performances of unpackaged and packaged devices are investigated.

This paper addresses the development of an energy-autonomous wireless vibration sensor for condition-based monitoring of machinery. Such technology plays an increasingly important role in modern manufacturing industry. In this work, energy harvesting is realized by resorting to a custom designed

We present a MEMS-based PZT/PZT thick film bimorph vibrationenergy harvester with an integrated silicon proof mass. The most common piezoelectric energy harvesting devices utilize a cantilever beam of a non piezoelectric material as support beneath or in-between the piezoelectric material...

Full Text Available This paper provides a state-of-the-art review of eigenstructure assignment methods for vibration cancellation. Eigenstructure assignment techniques have been widely used during the past three decades for vibration suppression in structures, especially in large space structures. These methods work similar to mode localization in which global vibrations are managed such that they remain localized within the structure. Such localization would help reducing vibrations more effectively than other methods of vibration cancellation, by virtue of confining the vibrations close to the source of disturbance. The common objective of different methods of eigenstructure assignment is to provide controller design freedom beyond pole placement, and define appropriate shapes for the eigenvectors of the systems. These methods; however, offer a large and complex design space of options that can often overwhelm the control designer. Recent developments in orthogonal eigenstructure control offers a significant simplification of the design task while allowing some experience-based design freedom. The majority of the papers from the past three decades in structuralvibration cancellation using eigenstructure assignment methods are reviewed, along with recent studies that introduce new developments in eigenstructure assignment techniques.

This thesis covers the structural, electronic, magnetic, and vibrational properties of graphene and silicene. In Chapter I, we will start with an introduction to graphene and silicene. In Chapter II, we will briefly discuss about the methodology (i

The objective of this research is to advance the state of the art of vibration control of mistuned periodic structures utilizing the electromechanical coupling and damping characteristics of piezoelectric networking...

The overall goal of this DURIP project is to acquire major facilities that are critical in the development of a comprehensive experimental testbed for advancing the technology of low vibration periodic structures (e.g...

Hybrid energy harvesters based on different physical effects is fascinating, but a rational design for multiple energy harvesting is challenging. In this work, a spring-magnet oscillator-based triboelectric-electromagnetic generator (EMG) with a solar cell cap is proposed. A power was produced by a triboelectric nanogenerator (TENG) and an EMG independently or simultaneously by using a shared spring-magnet oscillator. The oscillator configuration enables versatile energy harvesting with the excellent size scalability and self-packaged structure which can perform well at low frequency ranging from 3.5 to 5 Hz. The solar cell cap mounted above the oscillator can harvest solar energy. Under vibrations at the frequency of 4 Hz, the TENG and the EMG produced maximum output power of 5.46 nW cm-3 and 378.79 μW cm-3, respectively. The generated electricity by the hybrid nanogenerator can be stored in a capacitor or Li-ion battery, which is capable of powering a wireless locator for real-time locating data reporting to a personal cell phone. The light-weight and handy hybrid nanogenerator can directly light a caution light or play as a portable flashlight by shaking hands at night.

The propagation of torsional wave in the shaft with periodically attached local resonators is studied with the transfer matrix theory and the finite element method. The analytical dispersion relation and the complex band structure of such a structure is presented for the first time, which indicates the existence of low frequency gaps. The effect of shaft material on the vibration attenuation in band gap is investigated. The frequency response function of the shaft with finite periodic locally resonant oscillators is simulated with finite element method, which shows large vibration attenuation in the frequency range of the gap as expected. The low frequency torsional gap in shafts provides a new idea for vibration control

of active modal controllers. The main aim is to reduce vibrations in periodic time-varying structures. Special emphasis is given to vibration control of coupled bladed rotor systems. A state feedback modal control law is developed based on modal analysis in periodic time-varying structures. The first step...... in the procedure is a transformation of the model into a time-invariant modal form by applying the modal matrices, which are also periodic time-variant. Due to coupled rotor and blade motions complex vibration modes occur in the modal transformed state space model. This implies that the modal transformed model...

Full Text Available The paper contains investigations on element vibration of a real residential 9-storeyed reinforced-concrete frame building induced by train movement in the shallow subway. A design model for a problem on propagation of bending waves within the limits of the typical fragment of a skeleton is presented in the paper. The steady state vibrations of a column and reinforced-concrete slab induced by an excited force which is equivalent to the impact of the subway trains have been investigated in the paper. The problem has been solved numerically on the basis of the ANSYS FEA program. Numerical results have been compared with an approximate analytical solution and data on full-scale experiment. A prediction technique for vibration propagation in the designed buildings is offered in the paper.

This study investigates the vibration of a rotating piezoelectric device that consists of a proof mass that is supported by elastic structures with piezoelectric layers. Vibration of the proof mass causes deformation in the piezoelectric structures and voltages to power the electrical loads. The coupled electromechanical equations of motion are derived using Newtonian mechanics and Kirchhoff's circuit laws. The free vibration behavior is investigated for devices with identical (tuned) and nonidentical (mistuned) piezoelectric support structures and electrical loads. These devices have complex-valued, speed-dependent eigenvalues and eigenvectors as a result of gyroscopic effects caused by their constant rotation. The characteristics of the complex-valued eigensolutions are related to physical behavior of the device's vibration. The free vibration behaviors differ significantly for tuned and mistuned devices. Due to gyroscopic effects, the proof mass in the tuned device vibrates in either forward or backward decaying circular orbits in single-mode free response. This is proven analytically for all tuned devices, regardless of the device's specific parameters or operating speed. For mistuned devices, the proof mass has decaying elliptical forward and backward orbits. The eigenvalues are shown to be sensitive to changes in the electrical load resistances. Closed-form solutions for the eigenvalues are derived for open and close circuits. At high rotation speeds these devices experience critical speeds and instability.

This study concerns the effect of mechanical vibration applied simultaneously with inoculation (0,05% Nb) on the solidification structure of aluminium, with a view to refining the grain size. The results shows that the method used is an efficient way to control the final structure of the aluminium. The best results were found for low values of the frequencies of vibration and for the small amplitudes. (Author) [pt

Full Text Available A measurement bench has been developed to fully automate the procedure for the characterization of a vibration-based energy scavenging system. The measurement system is capable of monitoring all important characteristics of a vibration harvesting system (input and output voltage, current, and other parameters, frequency and acceleration values, etc.. It is composed of a PC, typical digital measuring instruments (oscilloscope, waveform generator, etc., certain sensors and actuators, along with a microcontroller based automation module. The automation of the procedure and the manipulation of the acquired data are performed by LabVIEW software. Typical measurements of a system consisting of a vibrating source, a vibration transducer and an active rectifier are presented.

A fluid finite element has been developed for a quasi-compressible fluid. Both kinetic and potential energy are expressed as functions of nodal displacements. Thus, the formulation is similar to that used for structural elements, with the only differences being that the fluid can possess gravitational potential, and the constitutive equations for fluid contain no shear coefficients. Using this approach, structural and fluid elements can be used interchangeably in existing efficient sparse-matrix structural computer programs such as SPAR. The theoretical development of the element formulations and the relationships of the local and global coordinates are shown. Solutions of fluid slosh, liquid compressibility, and coupled fluid-shell oscillation problems which were completed using a temporary digital computer program are shown. The frequency correlation of the solutions with classical theory is excellent.

Full Text Available To take advantage of applications where both light and vibrationenergy are available, a hybrid indoor ambient light and vibrationenergy harvesting scheme is proposed in this paper. This scheme uses only one power conditioning circuit to condition the combined output power harvested from both energy sources so as to reduce the power dissipation. In order to more accurately predict the instantaneous power harvested from the solar panel, an improved five-parameter model for small-scale solar panel applying in low light illumination is presented. The output voltage is increased by using the MEMS piezoelectric cantilever arrays architecture. It overcomes the disadvantage of traditional MEMS vibrationenergy harvester with low voltage output. The implementation of the maximum power point tracking (MPPT for indoor ambient light is implemented using analog discrete components, which improves the whole harvester efficiency significantly compared to the digital signal processor. The output power of the vibrationenergy harvester is improved by using the impedance matching technique. An efficient mechanism of energy accumulation and bleed-off is also discussed. Experiment results obtained from an amorphous-silicon (a-Si solar panel of 4.8 × 2.0 cm2 and a fabricated piezoelectric MEMS generator of 11 × 12.4 mm2 show that the hybrid energy harvester achieves a maximum efficiency around 76.7%.

This letter investigates the energy harvesting from the horizontal coherent resonance of a vertical cantilever beam subjected to the vertical base excitation. The potential energy of the system has two symmetric potential wells. So, under vertical excitation, the system can jump between two potential wells, which will lead to the large vibration in horizontal direction. Two piezoelectric patches are pasted to harvest the energy. From experiment, it is found that the vertical excitation can make the beam turn to be bistable. The system can transform vertical vibration into horizontal vibration of low frequency when excited by harmonic motion. The horizontal coherence resonance can be observed when excited by a vertical white noise. The corresponding output voltages of piezoelectric films reach high values.

We report differential cross section results from an experimental investigation into the electron impact excitation of a number of the low-lying composite (unresolved) vibrational modes in phenol (C{sub 6}H{sub 5}OH). The measurements were carried out at incident electron energies in the range 15–40 eV and for scattered-electron angles in the range 10–90°. The energy resolution of those measurements was typically ∼80 meV. Calculations, using the GAMESS code, were also undertaken with a B3LYP/aug-cc-pVDZ level model chemistry, in order to enable us to assign vibrational modes to the features observed in our energy loss spectra. To the best of our knowledge, the present cross sections are the first to be reported for vibrational excitation of the C{sub 6}H{sub 5}OH molecule by electron impact.

In the present paper, the ground state van der Waals potential of the Radon dimer is described by the Tang-Toennies potential model, which requires five essential parameters. Among them, the two dispersion coefficients C6 and C8 are estimated from the well determined dispersion coefficients C6 and C8 of Xe2. C10 is estimated by using the approximation equation that C6C10/C82 has an average value of 1.221 for all the rare gas dimers. With these estimated dispersion coefficients and the well determined well depth De and Re the Born-Mayer parameters A and b are derived. Then the vibrationalenergy levels of the ground state radon dimer are calculated. 40 vibrationalenergy levels are observed in the ground state of Rn2 dimer. The last vibrationalenergy level is bound by only 0.0012 cm-1.

This paper presents experiments and models of an energy harvesting device in which a low frequency resonator impacts a high frequency energy harvesting resonator, resulting in energy harvesting predominantly at the system's coupled vibration frequency. Analysis shows that a reduced mechanical damping ratio during coupled vibration enables increased electrical power generation as compared with conventional technology. Experiments demonstrate that the efficiency of electrical power transfer is significantly improved with the coupled vibration approach. An average power output of 0.43 mW is achieved under 0.4g acceleration at 8.2 Hz, corresponding to a power density of 25.5 µW cm −3 . The measured power and power density at the resonant frequency are respectively 4.8 times and 13 times the measured peak values for a conventional harvester created from a low frequency beam alone

In this work, we present a multimodal wideband vibrationenergy harvester designed to scavenge energy from ambient vibrations over a wide frequency range. The harvester consists of a folded cantilever, three magnetoelectric (ME) transducers, and two magnetic circuits. The folded cantilever enables multi-resonant response formed by bending of each stage, and the nonlinear magnetic forces acting on the folded cantilever beam allow further broadening of the frequency response. We also investigate the effects of the position of the ME transducer on the electrical output in order to achieve optimal performance. The experimental results show that the vibrationenergy harvester exhibited three resonance peaks in a range of 5 Hz to 30 Hz, a wider working bandwidth of 10.1 Hz, and a maximum average power value of 31.58 μW at an acceleration of 0.6 g (with g = 9.8 m/s2).

Coherent coupling between an optical transition and confined optical mode have been investigated for electronic-state transitions, however, only very recently have vibrational transitions been considered. Here, we demonstrate both static and dynamic results for vibrational bands strongly coupled to optical cavities. We experimentally and numerically describe strong coupling between a Fabry-Pérot cavity and carbonyl stretch ( 1730 cm 1) in poly-methylmethacrylate and provide evidence that the mixed-states are immune to inhomogeneous broadening. We investigate strong and weak coupling regimes through examination of cavities loaded with varying concentrations of a urethane monomer. Rabi splittings are in excellent agreement with an analytical description using no fitting parameters. Ultrafast pump-probe measurements reveal transient absorption signals over a frequency range well-separated from the vibrational band, as well as drastically modified relaxation rates. We speculate these modified kinetics are a consequence of the energy proximity between the vibration-cavity polariton modes and excited state transitions and that polaritons offer an alternative relaxation path for vibrational excitations. Varying the polariton energies by angle-tuning yields transient results consistent with this hypothesis. Furthermore, Rabi oscillations, or quantum beats, are observed at early times and we see evidence that these coherent vibration-cavity polariton excitations impact excited state population through cavity losses. Together, these results indicate that cavity coupling may be used to influence both excitation and relaxation rates of vibrations. Opening the field of polaritonic coupling to vibrational species promises to be a rich arena amenable to a wide variety of infrared-active bonds that can be studied in steady state and dynamically.

The primary means of inspecting buildings and other structures is to evaluate each structure member individually. This is a time consuming process that is expensive, particularly if sheathing or other covering materials must be removed to access the structural members. This paper presents an effort to use a low frequency vibration method for assessing the structural...

by the results of a harmonic analysis based on B3LYP/cc-pVTZ density functional theory (DFT). The combined experimental and theoretical results led to proposal of a nearly complete assignment of the fundamental vibrational transitions of DD, involving reassignment of several transitions. The results...

Full Text Available involved into rotation (precession) with respect to the inertial space with scale factors depending on nature of elastic modes and their numbers. Corresponding scales factors or Bryan’s factors of the vibrating mode’s precession are calculated depending...

This report summarizes the flow-induced vibration of circular cylinders in quiescent fluid, axial flow, and crossflow, and applications of the analytical methods and experimental data in design evaluation of various system components consisting of circular cylinders. 219 figs., 30 tabs

This paper provides a quantification of the changes in vibration level that can be expected in a lightweight multi-storey wooden building due to reduced connection stiffness or added nonstructural mass. Firstly, the impact of changes in the floor-to-wall connections is examined. Secondly, a study...

In this paper, active vibration control performance of the smart hull structure with macro-fiber composite (MFC) is evaluated. MFC is an advanced piezoelectric composite which has great flexibility and increased actuating performance compared to a monolithic piezoelectric ceramic patch. The governing equations of motion of the hull structure with MFC actuators are derived based on the classical Donnell–Mushtari shell theory. The actuating model for the interaction between hull structure and MFC is included in the governing equations. Subsequently, modal characteristics are investigated and compared with the results obtained from experiment. The governing equations of the vibration control system are then established and expressed in the state space form. A linear quadratic Gaussian (LQG) control algorithm is designed in order to effectively and actively control the imposed vibration. The controller is experimentally realized and vibration control performances are evaluated

The noise level is getting higher with the development of high-power marine power plant. Mechanical noise is one of the most obvious noise sources which not only affect equipment reliability, riding comfort and working environment, but also enlarge underwater noise. The periodic truss type device which is commonly applied in fields of aerospace and architectural is introduced to floating raft construction in ship. Four different raft frame structure are designed in the paper. The vibration transmissibility is taken as an evaluation index to measure vibration isolation effect. A design scheme with the best vibration isolation effect is found by numerical method. Plate type and the optimized periodic truss type raft frame structure are processed to experimental verify vibration isolation effect of the structure of the periodic raft. The experimental results demonstrate that the same quality of the periodic truss floating raft has better isolation effect than that of the plate type floating raft.

Full Text Available Piezoelectricity is a type of material that enables mechanical energy and electrical energy to be interchangeable, which can be divided into positive piezoelectric effect and inverse piezoelectric effect. The positive piezoelectric effect is that the electric dipole moment of material generates changes when the piezoelectric material is subjected to pressure, resulting in electrical energy. Conversely, the inverse piezoelectric effect is the process of electrical energy converted into mechanical energy.

In present study, the experimental and theoretical harmonic vibrational frequencies of gliclazide molecule have been investigated. The experimental FT-IR (400-4000 cm-1) and Laser-Raman spectra (100-4000 cm-1) of the molecule in the solid phase were recorded. Theoretical vibrational frequencies and geometric parameters (bond lengths and bond angles) have been calculated using ab initio Hartree Fock (HF), density functional theory (B3LYP hybrid function) methods with 6-311++G(d,p) and 6-31G(d,p) basis sets by Gaussian 09W program. The assignments of the vibrational frequencies were performed by potential energy distribution (PED) analysis by using VEDA 4 program. Theoretical optimized geometric parameters and vibrational frequencies have been compared with the corresponding experimental data, and they have been shown to be in a good agreement with each other. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies have been found.

This paper describes a relatively simple and quick method for implementing aerodynamic heating models into a finite element code for non-linear transient thermal-structural and thermal-structural-vibrational analyses of a Mach 10 generic HyShot scram-jet engine. The thermal-structural-vibrational response of the engine was studied for the descent trajectory from 60 to 26 km. Aerodynamic heating fluxes, as a function of spatial position and time for varying trajectory points, were implemented in the transient heat analysis. Additionally, the combined effect of varying dynamic pressure and thermal loads with altitude was considered. This aero-thermal-structural analysis capability was used to assess the temperature distribution, engine geometry distortion and yielding of the structural material due to aerodynamic heating during the descent trajectory, and for optimising the wall thickness, nose radius of leading edge, etc. of the engine intake. A structuralvibration analysis was also performed following the aero-thermal-structural analysis to determine the changes in natural frequencies of the structuralvibration modes that occur at the various temperatures associated with the descent trajectory. This analysis provides a unique and relatively simple design strategy for predicting and mitigating the thermal-structural-vibrational response of hypersonic engines. (authors)

Many complicated systems of practical interest consist basically of a well-defined outer shell-like master structure and a complicated internal structure with uncertain dynamic properties. Using the "fuzzy structure theory" for predicting audible frequency vibration, the internal structure......-dimensional continuous boundary. Additionally, a simple method for determining the so-called equivalent coupling factor is presented. The validity of this method is demonstrated by numerical simulations of the vibration response of a master plate structure with fuzzy attachments. It is revealed that the method performs...

This paper presents a new approach for vibration mitigation based on a dynamic vibration absorbing structure (DVAS) for electric vehicles (EVs) that use in-wheel switched reluctance motors (SRMs). The proposed approach aims to alleviate the negative effects of vibration caused by the unbalanced electromagnetic force (UMEF) that arises from road excitations. The analytical model of SRMs is first formulated using Fourier series, and then a model of the coupled longitudinal-vertical dynamics is developed taking into consideration the external excitations consisting of the aerodynamic drag force and road unevenness. In addition, numerical simulations for a conventional SRM-suspension system and two novel DVASs are carried out for varying road levels specified by ISO standards and vehicle velocities. The results of the comparison reveal that a 35% improvement in ride comfort, 30% improvement of road handling, and 68% improvement in air gap between rotor and stator can be achieved by adopting the novel DVAS compared to the conventional SRM-suspension system. Finally, multi-body simulation (MBS) is performed using LMS Motion to validate the feasibility of the proposed DVAS. Analysis of the results shows that the proposed method can augment the effective application of SRMs in EVs.

For NCS in the X ˜ 2 Π electronic ground state, three-dimensional potential energy surfaces (3D PESs) have been calculated ab initio at the core-valence, full-valence MR-SDCI+Q/[aug-cc-pCVQZ (N, C, S)] level of theory. The ab initio 3D PESs are employed in second-order-perturbation-theory and DVR3D calculations to obtain various molecular constants and ro-vibrationally averaged structures. The 3D PESs show that the X ˜ 2 Π NCS has its potential minimum at a linear configuration, and hence it is a "linear molecule." The equilibrium structure has re (N-C) = 1.1778 Å, re (C-S) = 1.6335 Å, and ∠e (N-C-S) = 180°. The ro-vibrationally averaged structure, determined as expectation values over DVR3D wavefunctions, has 〈 r (N-C)〉0 = 1.1836 Å, 〈 r (C-S)〉0 = 1.6356 Å, and 〈 ∠ (N-C-S)〉0 = 172.5°. Using these expectation values as the initial guess, a bent r0 structure having an 〈 ∠ (N-C-S)〉0 of 172.2° is deduced from the experimentally reported B0 values for NC32S and NC34S. Our previous prediction that a linear molecule, in any ro-vibrational state including the ro-vibrational ground state, is to be "observed" as being bent on ro-vibrational average, has been confirmed here theoretically through the expectation value for the bond-angle deviation from linearity, 〈 ρ bar 〉 , and experimentally through the interpretation of the experimentally derived rotational-constant values.

Thin polycrystalline films of hexatriacontane (HTC) were irradiated with low energy (E=0.5--15 eV) electrons, and off-specular backscattered electron spectra were measured. Below E∼7 eV, single and multiple vibrational excitations only are observed, which relax the electrons down to the bottom of the HTC conduction band. Due to the negative electron affinity of HTC, thermal electrons are emitted into vacuum. Structure in the backscattered electron current at kinetic energies about 1.5 and 4 eV are associated to conduction band density of states. Above E∼7 eV, the dominant losses correspond to electronic excitations, excitons, or above a threshold (energy of the electron inside the HTC film) at 9.2±0.1 eV, electron--hole pair generation. The latter process is very efficient and reaches a yield of the order of one ∼11 eV. Evidence for chemical reaction above E∼4 eV is observed

Full Text Available The Finite Element Method (FEM combined with the Frequency Averaged Quadratic Pressure method (FAQP are used to calculate the acoustic radiation of structures excited in the frequency band. The surface particle velocity of stiffened cylindrical shells under frequency band excitation is calculated using finite element software, the normal vibration velocity is converted from the surface particle velocity to calculate the average energy source (frequency averaged across intensity, frequency averaged across pressure and frequency averaged across velocity, and the FAQP method is used to calculate the average sound pressure level within the bandwidth. The average sound pressure levels are then compared with the bandwidth using finite element and boundary element software, and the results show that FEM combined with FAQP is more suitable for high frequencies and can be used to calculate the average sound pressure level in the 1/3 octave band with good stability, presenting an alternative to applying frequency-by-frequency calculation and the average frequency process. The FEM/FAQP method can be used as a prediction method for calculating acoustic radiation while taking the randomness of vibration at medium and high frequencies into consideration.

This paper discusses the development and testing of a renewable energy source for powering wireless sensors used to monitor the structural health of bridges. Traditional power cables or battery replacement are excessively expensive or infeasible in this type of application. An inertial power generator has been developed that can harvest traffic-induced bridge vibrations. Vibrations on bridges have very low acceleration (0.1–0.5 m s −2 ), low frequency (2–30 Hz), and they are non-periodic. A novel parametric frequency-increased generator (PFIG) is developed to address these challenges. The fabricated device can generate a peak power of 57 µW and an average power of 2.3 µW from an input acceleration of 0.54 m s −2 at only 2 Hz. The generator is capable of operating over an unprecedentedly large acceleration (0.54–9.8 m s −2 ) and frequency range (up to 30 Hz) without any modifications or tuning. Its performance was tested along the length of a suspension bridge and it generated 0.5–0.75 µW of average power without manipulation during installation or tuning at each bridge location. A preliminary power conversion system has also been developed

It is of interest to have analytical methodologies available for the dynamic behavior of large mechanical structures like those in thermal cycle systems of nuclear power plants or in transport systems during the experimental stage prior to their construction, as happens in aeronautics, where prototypes are tested in experimental banks on a scale of 1 to 1. The same does not occur with systems for the generation of electrical energy such as a nuclear power plant or in ships, competition automobiles, railway systems, etc. Not because of the technical impossibility but because of the high costs involved. This work aims to implement a technology based on the analysis of the vibrations to obtain a profile of the modal dynamic response and its influence on the critical components of the mechanisms with the particularity of detecting the preventive location of the component that may suffer a potential damage. The Vibrations Analysis Laboratory has resolved different cases in the Embalse Nuclear Plant, in the Atucha Nuclear Plant, in the Heavy Water Industrial Plant, in the automobile industry and in other industrial areas (CW)

The present Calspan experiments have shown direct evidence of preferential vibrational pumping of two heavy isotopes of CO: 13 C 16 O and 12 C 18 O. The nature of the enhancement is generally consistent with the predictions of theoretical modeling. These are the first direct experimental demonstrations of this isotope selection method. The potential advantages of such a means of isotope separation are inherent in the V-V pumping process itself. Summarizing these: (1) Selectivity actually increases at higher reactant pressures, since the selection mechanism is collisional. Accordingly, rather high throughputs are possible, unlike other techniques in which molecular collisions actually decrease selectivity. (2) A variety of excitation methods can potentially be used - electric discharge, optical excitation by coherent or incoherent sources, or chemical excitation; laser excitation is not critical to the process. (3) The method can be applied to many isotopes of the lighter atoms. It is not inherently species-specific

A wirelessly powered remote sensor node is presented along with its design process. The purpose of the node is the further expansion of the sensing capabilities of the commercial Perpetuum system used for condition monitoring on trains and rolling stock which operates using vibrationenergy harvesting. Surplus harvested vibrationenergy is transferred wirelessly to a remote satellite sensor to allow measurements over a wider area to be made. This additional data is to be used for long term condition monitoring. Performance measurements made on the prototype remote sensor node are reported and advantages and disadvantages of using the same RF frequency for power and data transfer are identified.

Full Text Available The connection of two building structures with dampers is one of effective vibration control systems. In this vibration control system, both buildings have to possess different vibration properties in order to provide a higher vibration reduction performance. In addition to such condition of different vibration properties of both buildings, the connecting dampers also play an important role in the vibration control mechanism. In this paper, the effect of nonlinearity of connecting dampers on the vibration control of connected building structures is investigated in detail. A high-damping rubber damper and an oil damper with and without relief mechanism are treated. It is shown that, while the high-damping rubber damper is effective in a rather small deformation level, the linear oil damper is effective in a relatively large deformation level. It is further shown that, while the oil dampers reduce the response in the same phase as the case without dampers, the high-damping rubber dampers change the phase. The merit is that the high-damping rubber can reduce the damper deformation and keep the sufficient space between both buildings. This can mitigate the risk of building pounding.

The vibration-based monitoring of flexible civil structures and performance evaluation from this monitoring are reviewed, with an emphasis on research and practice in Japan and the author’s experiences. Some new findings and unexpected vibrations from the monitoring of real bridges and buildings are reported to emphasize the importance of monitoring. Future developments and applications of vibration-based monitoring to civil infrastructure management are also described. Many examples are taken from the author’s past 30 years’ experience of research on bridge dynamics. PMID:29434082

Fluid-elastic instability (FEI) in tube bundle heat exchangers was studied experimentally. The motion of an array of 15 stainless steel vibrating tubes (Φ 25.4mm) in water cross-flow, suspended using stainless steel piano wire has been recorded with a CCD camera. The individual motion and relative motion of the tubes are reported and can be used for computational model validation. The relative displacement of the tubes allows identification of the most potentially damaging patterns of tube bundle vibration. A critical reduced velocity may be determined by specification of an allowable limit on tube motion amplitude. Measurements were made for various tube array configurations, tube natural frequencies and flow conditions. (author)

The crystals of the new melaminium arsenate (MAS) [C3H7N6+ṡH2AsO4-] were obtained by the slow evaporation of an aqueous solution at room temperature. Single crystal X-ray diffraction analysis reveals that the crystal belongs to triclinic system with centro symmetric space group P-1. The crystals are built up from single protonated melaminium residues and single dissociated arsenate H2AsO4- anions. The protonated melaminium ring is almost planar. A combination of ionic and donor-acceptor hydrogen-bond interactions linking together the melaminium and arsenate residues forms a three-dimensional network. Vibrational spectroscopic analysis is reported on the basis of FT-IR and FT-Raman spectra recorded at room temperature. Hydrogen bonded network present in the crystal gives notable vibrational effect. DSC has also been performed for the crystal shows no phase transition in the studied temperature range (113-293 K).

Vibrational kinetic and spectroscopic studies have been performed on matrix-isolated HCl and DCl between 9 and 20 K. Vibrational relaxation rates for v = 2 and v = 1 were measured by a tunable infrared laser-induced, time-resolved fluorescence technique. In an Ar matrix, vibrational decay times are faster than radiative and it is found that HCl relaxes about 35 times more rapidly than CCl, in spite of the fact that HCl must transfer more energy to the lattice than DCl. This result is explained by postulating that the rate-determining step for vibrational relaxation produces a highly rotationally excited guest in a V yield R step; rotational relaxation into lattice phonons follows rapidly. HCl v = 1, but not v = 2, excitation rapidly diffuses through the sample by a resonant dipole-dipole vibrationalenergy transfer process. Molecular complexes, and in particular the HCl dimer, relax too rapidly for direct observation, less than or approximately 1 ..mu..s, and act as energy sinks in the energy diffusion process. The temperature dependence for all these processes is weak--less than a factor of two between 9 and 20 K. Vibrational relaxation of HCl in N/sub 2/ and O/sub 2/ matrices is unobservable, presumably due to rapid V yield V transfer to the host. A V yield R binary collision model for relaxation in solids is successful in explaining the HCl(DCl)/Ar results as well as results of other experimenters. The model considers relaxation to be the result of ''collisions'' due to molecular motion in quantized lattice normal modes--gas phase potential parameters can fit the matrix kinetic data.

Vibrational kinetic and spectroscopic studies have been performed on matrix-isolated HCl and DCl between 9 and 20 K. Vibrational relaxation rates for v = 2 and v = 1 were measured by a tunable infrared laser-induced, time-resolved fluorescence technique. In an Ar matrix, vibrational decay times are faster than radiative and it is found that HCl relaxes about 35 times more rapidly than CCl, in spite of the fact that HCl must transfer more energy to the lattice than DCl. This result is explained by postulating that the rate-determining step for vibrational relaxation produces a highly rotationally excited guest in a V yield R step; rotational relaxation into lattice phonons follows rapidly. HCl v = 1, but not v = 2, excitation rapidly diffuses through the sample by a resonant dipole-dipole vibrationalenergy transfer process. Molecular complexes, and in particular the HCl dimer, relax too rapidly for direct observation, less than or approximately 1 μs, and act as energy sinks in the energy diffusion process. The temperature dependence for all these processes is weak--less than a factor of two between 9 and 20 K. Vibrational relaxation of HCl in N 2 and O 2 matrices is unobservable, presumably due to rapid V yield V transfer to the host. A V yield R binary collision model for relaxation in solids is successful in explaining the HCl(DCl)/Ar results as well as results of other experimenters. The model considers relaxation to be the result of ''collisions'' due to molecular motion in quantized lattice normal modes--gas phase potential parameters can fit the matrix kinetic data

Heat transfer enhancement is an important issue in energy systems. To improve the efficiency of a cooling channel used inside injection molds, turbine blades, and high-temperature devices, channels with various shapes, such as wavy, elliptical, and twisted, have been studied. A cooling channel with a partially wavy inner structure has shown outstanding cooling performance despite a small increase in friction factor. However, generating a partially wavy inner structure inside a channel through conventional machining processes is not easy. To address this problem, we developed a new process called Perpendicular vibration-induced electrical discharge machining (PV-EDM). A specific electrode and one- and random-directional vibrating devices controlled by a pneumatic load were designed for the PV-EDM process. Experimental results showed that local shaping on the inner wall of a channel is possible, which confirmed the possibility of application of this process to actual industrial problems.

The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective.

The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective

The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective.

Most equipments, piping systems and reactor structures in nuclear power plants are subjected to flow induced vibration due to high temperature and high pressure coolant flowing inside or outside of the equipments, systems and structures. Because the flow induced vibration sometimes causes significant damage to reactor structures and piping systems, it is important and necessary to evaluate the vibration effect on them and to prove their structural integrity. Korea Multipurpose Research Reactor (KMRR) being constructed by KAERI is 30 MWt pool type research reactor. Since its main structures and piping systems were designed and manufactured in accordance with the standards and guidelines for commercial nuclear power plant, it was decided to evaluate their vibratory response in accordance with the standards and guidelines for commercial NPP. The objective of this vibration test is the assessment of vibration levels of KMRR reactor structure and primary cooling piping system for their structural integrity under the steady-state or transient operating condition. 38 figs, 14 tabs, 2 refs. (Author).

Most equipments, piping systems and reactor structures in nuclear power plants are subjected to flow induced vibration due to high temperature and high pressure coolant flowing inside or outside of the equipments, systems and structures. Because the flow induced vibration sometimes causes significant damage to reactor structures and piping systems, it is important and necessary to evaluate the vibration effect on them and to prove their structural integrity. Korea Multipurpose Research Reactor (KMRR) being constructed by KAERI is 30 MWt pool type research reactor. Since its main structures and piping systems were designed and manufactured in accordance with the standards and guidelines for commercial nuclear power plant, it was decided to evaluate their vibratory response in accordance with the standards and guidelines for commercial NPP. The objective of this vibration test is the assessment of vibration levels of KMRR reactor structure and primary cooling piping system for their structural integrity under the steady-state or transient operating condition. 38 figs, 14 tabs, 2 refs. (Author)

The vibration control and health monitoring of building structures have been actively investigated in recent years but often treated separately according to the primary objective pursued. In this study, a time-domain integrated vibration control and health monitoring approach is proposed based on the extended Kalman filter (EKF) for identifying the physical parameters of the controlled building structures without the knowledge of the external excitation. The physical parameters and state vectors of the building structure are then estimated and used for the determination of the control force for the purpose of the vibration attenuation. The interaction between the health monitoring and vibration control is revealed and assessed. The feasibility and reliability of the proposed approach is numerically demonstrated via a five-story shear building structure equipped with magneto-rheological (MR) dampers. Two types of excitations are considered: (1) the EI-Centro ground excitation underneath of the building and (2) a swept-frequency excitation applied on the top floor of the building. Results show that the structural parameters as well as the unknown dynamic loadings could be identified accurately; and, at the same time, the structuralvibration is significantly reduced in the building structure. (paper)

The present paper describes the fundamental feature of the fluid-elastic vibration of flexible overflow weir, as observed in the French demonstration fast breeder reactor, Super Phenix-1. In the experimental study, the instability criterion of the fluid-elastic vibration was studied by using a simple experimental apparatus of a rectangular tank separated by a flexible weir. A spring-mass model was developed to clarify the mechanism of the instability. The instability condition was analytically derived from the equations of the spring-mass model. The equations of the spring-mass model was also computationally integrated in time to simulate the temporal evolution of the fluid-elastic vibration. The comparison between the experimental and theoretical results indicates that the present theoretical model is capable of predicting most of the physical tendencies observed in the experiment. The present study revealed that the lag time of waterfall at the weir is the most influential parameter among other hydro-elastic parameters. (author)

Full Text Available This paper presents a procedure of determining the causes of increased vibration of a fan plant and its support structure in the PUC 'Subotička toplana'. Excessive vibrations were observed following the installation of the frequency converter, thus a methodological approach of testing-analysis-diagnosis has been applied. Based on the definition of the causes of this problem, the paper also suggests possible repair procedures.

Full Text Available Nonlinear magnetic forces are always used to enlarge resonant bandwidth of vibrationenergy harvesting systems with piezoelectric cantilever beams. However, how to determine properly the distance between two magnets is one of the key engineering problems. In this paper, the Melnikov theory is introduced to overcome it. Firstly, the Melnikov state-space model of the nonlinear piezoelectric vibrationenergy harvesting (PVEH system is built. Based on it, chaotic dynamics mechanisms of achieving broadband PVEH by nonlinearity are exposed by potential function of the unperturbed nonlinear PVEH system. Then the corresponding Melnikov function of the nonlinear PVEH system is defined, based on which two Melnikov necessary conditions of determining the distance are obtained. Finally, numerical simulations are done to testify the theoretic results. The results demonstrate that the distance is closely related to the excitation amplitude and frequency once geometric and material parameters are fixed. Under a single-frequency excitation, the nonlinear PVEH system can generate a periodic vibration around a stable point, a large-amplitude vibration around two stable points, or a chaotic vibration. The proposed method is very valuable for optimally designing and utilizing nonlinear broadband PVEH devices in engineering applications.

Isotopic substitution of muonium for hydrogen provides an unparalleled opportunity to deepen our understanding of quantum mass effects on chemical reactions. A recent topical review in this journal of the thermal and vibrationally state-selected reaction of Mu with H2 raises a number of issues that are addressed here. We show that some earlier quantum mechanical calculations of the Mu + H2 reaction, which are highlighted in this review, and which have been used to benchmark approximate methods, are in error by as much as 19% in the low-temperature limit. We demonstrate that an approximate treatment of the Born-Oppenheimer diagonal correction that was used in some recent studies is not valid for treating the vibrationally state-selected reaction. We also discuss why vibrationally adiabatic potentials that neglect bend zero-point energy are not a useful analytical tool for understanding reaction rates, and why vibrationally non-adiabatic transitions cannot be understood by considering tunnelling through vibrationally adiabatic potentials. Finally, we present calculations on a hierarchical family of potential energy surfaces to assess the sensitivity of rate constants to the quality of the potential surface.

Full Text Available This paper proposes an electric power self-supply module for the wireless sensor network (WSN sensor node. The module includes an electromagnetic vibrationenergy harvester based on micro-electro-mechanical system (MEMS technology and a processing circuit. The vibrationenergy harvester presented in this paper is fabricated by an integrated microfabrication process and consists of four similar and relatively independent beam vibration elements. The main functions of the processing circuit are to convert the output of the harvester from unstable alternating current (AC to stable direct current (DC, charge the super capacitor, and ensure the stable output of the super capacitor. The preliminary test results of the harvester chip show that the chip can output discontinuous pulse voltage, and the range of the voltage value is from tens to hundreds of millivolts in the vibration frequency range of 10–90 Hz. The maximum value that can be reached is 563 mV (at the vibration frequency of 18 Hz. The results of the test show that the harvester can output a relatively high voltage, which can meet the general electric power demand of a WSN sensor node.

The V ..-->.. T, R relaxation rate for NH/sub 3/ (..nu../sub 2/) was studied from 198/sup 0/K to 398/sup 0/K by the method of laser-excited vibrational fluorescence. The self-deactivation rate constant decreases from 2.4 ..mu..sec torr/sup -1/ at 198/sup 0/K to 0.65 ..mu..sec/sup -1/ torr/sup -1/ at 398/sup 0/K. The rate constants for deactivation by He, Ar, N/sub 2/, and O/sub 2/ are much smaller and show a weak temperature dependence in the opposite direction. The vibrational relaxation rates of the coupled ..nu../sub 1/, ..nu../sub 3/ stretching level manifold and of the 2..nu../sub 2/ bending level in H/sub 2//sup 18/O was studied from 250/sup 0/K to 400/sup 0/K using th same method as for NH/sub 3/. The ..nu../sub 1/, ..nu../sub 3/ self-deactivation rate goes from 1.4 ..mu..sec/sup -1/ torr/sup -1/ at 250/sup 0/K to 0.48 ..mu..sec-/sup 1/ torr-/sup 1/ at 400/sup 0/K. For 2..nu../sub 2/ it goes from 4.5 ..mu..sec-/sup 1/ torr to 1.9 ..mu..sec/sup -1/ torr/sup -1/. The temperature dependence of the deactivation of both levels by He and Ar is much weaker and the rates are several hundred times slower. Deactivation of ..nu../sub 1/, ..nu../sub 3/ by N/sub 2/, O/sub 2/, and CO/sub 2/ is measured only at 293/sup 0/K. N/sub 2/ and O/sub 2/ deactivate ..nu../sub 1/, ..nu../sub 3/ about 5 and CO/sub 2/ about 50 times faster than He or Ar.

In this paper, a control strategy is presented and numerically tested. This strategy aims to achieve the potential performance of fully active systems with a reduced energy supply. These energy needs are expected to be comparable to the power demands of semi-active systems, while system performance is intended to be comparable to that of a fully active configuration. The underlying strategy is called 'global semi-active control'. This control approach results from an energy investigation based on management of the optimal control process. Energy management encompasses storage and convenient restitution. The proposed strategy monitors a given active law without any external energy supply by considering purely dissipative and energy-demanding phases. Such a control law is offered here along with an analysis of its properties. A suboptimal form, well adapted for practical implementation steps, is also given. Moreover, a number of numerical experiments are proposed in order to validate test findings.

In this paper, a control strategy is presented and numerically tested. This strategy aims to achieve the potential performance of fully active systems with a reduced energy supply. These energy needs are expected to be comparable to the power demands of semi-active systems, while system performance is intended to be comparable to that of a fully active configuration. The underlying strategy is called 'global semi-active control'. This control approach results from an energy investigation based on management of the optimal control process. Energy management encompasses storage and convenient restitution. The proposed strategy monitors a given active law without any external energy supply by considering purely dissipative and energy-demanding phases. Such a control law is offered here along with an analysis of its properties. A suboptimal form, well adapted for practical implementation steps, is also given. Moreover, a number of numerical experiments are proposed in order to validate test findings

A passive-type dynamic vibration absorber (DVA) is basically a mass-spring system that suppresses the vibration of a structure at a particular frequency. Since the natural frequency of the DVA is usually tuned to a frequency of particular excitation, the DVA is especially effective when the excitation frequency is close to the natural frequency of the structure. Fixing the physical properties of the DVA limits the application to a narrowband, harmonically excited vibration problem. A frequency-tunable DVA that can modulate its stiffness provides adaptability to the vibration control device against non-stationary disturbances. In this paper, we suggest a broadband frequency-tunable DVA whose natural frequency can be extended by 300% to the nominal value using the magnetorheological elastomers (MREs). The frequency adjustability of the proposed absorber is first shown. The real-time vibration control performance of the frequency-tunable absorber for an acoustically excited plate having multiple resonant peaks is then evaluated. Investigations show that the vibration of the structure can be effectively reduced with an improved performance by the DVA in comparison to the conventional passive- type absorber. (paper)

The endothermic reactions Br + CH 3 I → CH 3 + IBr (ΔH 0 0 = 13 kcal/mole) and Br + CF 3 I → CF 3 + IBr (ΔH 0 0 = 11 kcal/mole) have been studied by the crossed molecular beams method. Detailed center-of-mass contour maps of the IBr product flux as a function of recoil velocity and scattering angle are derived. For both systems it is found that the IBr product is sharply backward scattered with respect to the incident Br dirction, and that most of the available energy goes into product translation. Vibrational enhancement of the Br + CF 3 I reaction was investigated by using the infrared multiphoton absorption process to prepare highly vibrationally excited CF 3 I. At a collision energy of 31 kcal/mole (several times the barrier height), reagent vibrationalenergy appears to be less effective than an equivalent amount of (additional) translational energy in promoting reaction. More forward scattered IBr is produced in reactions of Br with vibrationally hot CF 3 I

Full Text Available The piezoelectric systems of electric energy harvesting with an adaptive low-frequency resonance are developed. These systems allowed to obtain electricity from low-frequency vibration. The availability of their application for adaptation to other periodic processes including pedestrians and vehicles movement is shown.

The endothermic reactions Br + CH/sub 3/I ..-->.. CH/sub 3/ + IBr (..delta..H/sub 0//sup 0/ = 13 kcal/mole) and Br + CF/sub 3/I ..-->.. CF/sub 3/ + IBr (..delta..H/sub 0//sup 0/ = 11 kcal/mole) have been studied by the crossed molecular beams method. Detailed center-of-mass contour maps of the IBr product flux as a function of recoil velocity and scattering angle are derived. For both systems it is found that the IBr product is sharply backward scattered with respect to the incident Br dirction, and that most of the available energy goes into product translation. Vibrational enhancement of the Br + CF/sub 3/I reaction was investigated by using the infrared multiphoton absorption process to prepare highly vibrationally excited CF/sub 3/I. At a collision energy of 31 kcal/mole (several times the barrier height), reagent vibrationalenergy appears to be less effective than an equivalent amount of (additional) translational energy in promoting reaction. More forward scattered IBr is produced in reactions of Br with vibrationally hot CF/sub 3/I.

A method designed to measure relative ion—molecule reaction rates at thermal collision energies for selected reactant ion vibrational states is described. Relative reaction rates are determined for the three endothermic reactions: H2+ (υ)(He,H)HeH+, H2+ (υ)(Ne,H)NeH+, D2+(υ)(Ne, D)NeD+, and for the

Vibrationenergy harvesting is now receiving more interest as a means for powering intelligent wireless sensor systems. In this paper, a resonant electromagnetic vibrationenergy harvester (VEH) employing double cantilever to convert low-frequency vibrationenergy into electrical energy is presented. The VEH is made up of two cantilever beams, a coil, and magnetic circuits. The electric output performances of the proposed electromagnetic VEH have been investigated. With the enhancement of turns number N, the optimum peak power of electromagnetic VEH increases sharply and the resonance frequency deceases gradually. When the vibration acceleration is 0.5 g, we obtain the optimum output voltage and power of 9.04 V and 50.8 mW at frequency of 14.9 Hz, respectively. In a word, the prototype device was successfully developed and the experimental results exhibit a great enhancement in the output power and bandwidth compared with other traditional electromagnetic VEHs. Remarkably, the proposed resonant electromagnetic VEH have great potential for applying in intelligent wireless sensor systems.

This paper explores the concept of an acoustic black hole (ABH) as a main design framework for performing dynamic structural tailoring of mechanical systems for vibrationenergy harvesting applications. The ABH is an integral feature embedded in the host structure that allows for a smooth reduction of the phase velocity, theoretically approaching zero, while minimizing the reflected energy. This mechanism results in structural areas with high energy density that can be effectively exploited to develop enhanced vibration-based energy harvesting. Fully coupled electro-mechanical models of an ABH tapered structure with surface mounted piezo-transducers are developed to numerically simulate the response of the system to both steady state and transient excitations. The design performances are numerically evaluated using structural intensity data as well as the instantaneous voltage/power and energy output produced by the piezo-transducer network. Results show that the dynamically tailored structural design enables a drastic increase in the harvested energy as compared to traditional structures, both under steady state and transient excitation conditions. (papers)

The use of shunted piezoelectric patches in reducing vibration and sound radiation of structures has several advantages over passive viscoelastic elements, e.g., lower weight with increased controllability. The performance of the piezoelectric patches depends on the shunting electronics that are designed to dissipate vibrationenergy through a resistive element. In past efforts most of the proposed tuning methods were based on modal properties of the structure. In these cases, the tuning applies only to one mode of interest and maximum tuning is limited to invariant points when based on den Hartog's invariant points concept. In this study, a design method based on the wave propagation approach is proposed. Optimal tuning is investigated depending on the dynamic and geometric properties that include effects from boundary conditions and position of the shunted piezoelectric patch relative to the structure. Active filters are proposed as shunting electronics to implement the tuning criteria. The developed tuning methods resulted in superior capabilities in minimizing structuralvibration and noise radiation compared to other tuning methods. The tuned circuits are relatively insensitive to changes in modal properties and boundary conditions, and can applied to frequency ranges in which multiple modes have effects.

A transformation of potential energy surfaces (PES) being represented by multi-mode expansions is introduced, which allows for the calculation of anharmonic vibrational spectra of any isotopologue from a single PES. This simplifies the analysis of infrared spectra due to significant CPU-time savings. An investigation of remaining deviations due to truncations and the so-called multi-level approximation is provided. The importance of vibrational-rotational couplings for small molecules is discussed in detail. In addition, an analysis is proposed, which provides information about the quality of the transformation prior to its execution. Benchmark calculations are provided for a set of small molecules.

Mounting systems for structural members, fastening assemblies thereof, and vibration isolation systems including the same are provided. Mounting systems comprise a pair of mounting brackets, each clamped against a fastening assembly forming a mounting assembly. Fastening assemblies comprise a spherical rod end comprising a spherical member having a through opening and an integrally threaded shaft, first and second seating members on opposite sides of the spherical member and each having a through opening that is substantially coaxial with the spherical member through opening, and a partially threaded fastener that threadably engages each mounting bracket forming the mounting assembly. Structural members have axial end portions, each releasably coupled to a mounting bracket by the integrally threaded shaft. Axial end portions are threaded in opposite directions for permitting structural member rotation to adjust a length thereof to a substantially zero strain position. Structural members may be vibration isolator struts in vibration isolation systems.

This paper describes the characterization of thin-film MEMS vibrationenergy harvesters based on aluminum nitride as piezoelectric material. A record output power of 85 µW is measured. The parasitic-damping and the energy-harvesting performances of unpackaged and packaged devices are investigated. Vacuum and atmospheric pressure levels are considered for the packaged devices. When dealing with packaged devices, it is found that vacuum packaging is essential for maximizing the output power. Therefore, a wafer-scale vacuum package process is developed. The energy harvesters are used to power a small prototype (1 cm 3 volume) of a wireless autonomous sensor system. The average power consumption of the whole system is less than 10 µW, and it is continuously provided by the vibrationenergy harvester

We describe fabrication and characterization of a significantly improved version of a MEMS-based PZT/PZT thick film bimorph vibrationenergy harvester with an integrated silicon proof mass. The main advantage of bimorph vibrationenergy harvesters is that strain energy is not lost in mechanical...... support materials since only PZT is strained, and thus it has a potential for significantly higher output power. An improved process scheme for the energy harvester resulted in a robust fabrication process with a record high fabrication yield of 98.6%. Moreover, the robust fabrication process allowed...... a high pressure treatment of the screen printed PZT thick films prior to sintering, improving the PZT thick film performance and harvester power output reaches 37.1 μW at 1 g....

Vibration-based energy harvesters using piezoelectric materials have long made use of the cantilever beam structure. Surmounting the deficiencies in one-dimensional cantilever-based energy harvesters has been a major focus in the literature. In this work, we demonstrate a strategy of using two-dimensional beam shapes to harvest energy from low frequency excitations. A characteristic Zigzag-shaped beam is created to compare against the two proposed two-dimensional beam shapes, all of which occupy a 25.4 × 25.4 mm{sup 2} area. In addition to maintaining the low-resonance bending frequency, the proposed beam shapes are designed with the goal of realizing a concentrated stress structure, whereby stress in the beam is concentrated in a single area where a piezoelectric layer may be placed, rather than being distributed throughout the beam. It is shown analytically, numerically, and experimentally that one of the proposed harvesters is able to provide significant increase in power production, when the base acceleration is set equal to 0.1 g, with only a minimal change in the resonant frequency compared to the current state-of-the-art Zigzag shape. This is accomplished by eliminating torsional effects, producing a more pure bending motion that is necessary for high electromechanical coupling. In addition, the proposed harvesters have a large effective beam tip whereby large tip mass may be placed while retaining a low-profile, resulting in a low volume harvester and subsequently large power density.

I.R. and Raman spectra are reported for the following three systems: Ba2CaMo1−xTexO6, Ba2−xSrxMgWO6 and Ba2Ca1−xMgxWO6. In the first series the internal vibrations of the M6+O6 octahedra do not influence each other. The intensity of ν1 (MoO6) is five times that of ν1 (TeO6). In the second system

A coupled dynamic problem of electro-mechanics for a layered beam is formulated based on the Kirchhoff-Love hypotheses. In the case of harmonic loading, a simplified formulation is given using the single frequency approximation and the concept of complex moduli. As an example, the problem of forced vibration of a three-layer sandwich beam (aluminium alloy core covered with piezoelectric layers) with hinged ends is solved in order to investigate the accuracy and applicability of the approximate monoharmonic approach. Different aspects of the beam response to the mechanical and electric excitation are studied.

, a MATLAB toolbox (the ABRAVIBE toolbox) has been developed as an accompanying toolbox for the recent book "Noise and Vibration Analysis" by the author. This free, open software, published under GNU Public License, can be used with GNU Octave, if an entirely free software platform is wanted, with a few...... functional limitations. The toolbox includes functionality for simulation of mechanical models as well as advanced analysis such as time series analysis, spectral analysis, frequency response and correlation function estimation, modal parameter extraction, and rotating machinery analysis (order tracking...

National Aeronautics and Space Administration — Wireless sensors show enormous promise for safety improvements and cost reductions in monitoring the structural health of aircraft and spacecraft. A significant...

tions of potential energy surface (PES) for BrH2 system are more ... rier heights for both the exchange and abstraction are smaller than ... The complete picture on the dynamics of ..... Kurosaki Y and Takayanagi T private communication. 20.

The full quantum theory of dissociation processes in polyatomic molecules is converted to a form enabling the isolation of a selected fragment vibration. This form enables the easy evaluation of the probability distribution for energy partitioning between this vibration and all other degrees of freedom that results from the sudden Franck--Condon rearrangement process. The resultant Franck--Condon factors involve the square of the one-dimensional overlap integral between effective oscillator wavefunctions and the wavefunctions for the selected fragment vibration, a form that resembles the simple golden rule model for polyatomic dissociation and reaction processes. The full quantum theory can, therefore, be viewed as providing both a rigorous justification for certain generic aspects of the simple golden rule model as well as providing a number of important generalizations thereof. Some of these involve dealing with initial bound state vibrational excitation, explicit molecule, fragment and energy dependence of the effective oscillator, and the incorporation of all isotopic dependence. In certain limiting situations the full quantum theory yields simple, readily usable analytic expressions for the frequency and equilibrium position of the effective oscillator. Specific applications are presented for the direct photodissociation of HCN, DCN, and CO 2 where comparisons between the full theory and the simple golden rule are presented. We also discuss the generalizations of the previous theory to enable the incorporation of effects of distortion in the normal modes as a function of the reaction coordinate on the repulsive potential energy surface

Graphical abstract: Mechanisms of IVR in multi-tiers of intramolecular energy levels in different molecular environments are investigated. - Abstract: Transient femtosecond-IR-pump-UV-absorption probe-spectroscopy has been employed to shed light on the nature of intramolecular vibrationalenergy transfer (IVR) in dense molecular environments ranging from the diluted gas phase to the liquid. A general feature in our experiments and those of others is that IVR proceeds via multiple timescales if overtones or combination vibrations of high frequency modes are excited. It has been found that collisions enhance IVR if its (slower) timescales can compete with collisions. This enhancement is, however, much more weaker and rather inefficient as opposed to the effect of collisions on intermolecular energy transfer which is well known. In a series of experiments we found that IVR depends not significantly on the average energy transferred in a collision but rather on the number of collisions. The collisions are much less efficient in affecting IVR than VET. We conclude that collision induced broadening of vibrationalenergy levels reduces the energy gaps and enhances existing couplings between tiers. The present results are an important step forward to rationalize and understand apparently different and not consistent results from different groups on different molecular systems between gas and liquid phases.

of lightly damped structures are found on two branches, with the highest amplification branch on the low-frequency branch. The effect free wind turbulence is to destabilize the vibrations on the high amplification branch, thereby reducing the oscillation amplitude. The effect is most pronounced for very...

Nowadays, there are increasing use of very thin, subtle and light structures in the field of building constructions. We can find such a structures as part of roofs or design facades. By using these lamellas like, non-bearing structures as a part of architectural design of buildings, it is necessary to consider wind effects on these structures. Subtle structures of this type are prone to vibration in the transverse direction of the wind flow. The fact that the vibration occurs depends on wind parameters (wind velocity, direction of an air flow) and it also depends on the properties of lamella (shape, length, mass, natural frequency, support type). The principal idea of this article is to show susceptibility of lamellae-like structures to transverse resonant vibration caused by the phenomenon called Von Karman effect. Comparison of susceptibility to transverse resonance vibration was analysed on the different shapes of lamellas loaded by different wind speed. Analysis was based on usage of empirically derived equations. Von Karman effect arise from wind flow past an object. Turbulence in the form of vortices are formed at the object and shed into the flowing stream intermittently. The potential problem is that this turbulence can induce vibrations into the lamella itself. In terms of this vibration problem, two frequencies are interesting. Von Karman shedding frequency is the frequency at which the vortices are formed and shed at the object. The vortex-shedding frequency increases with the velocity of the wind flow and decreases with the size of the object. Natural frequency of the object depends on the construction of the lamella itself. Parameters of lamella as a shape, mass, length, elasticity modulus of material and support types are directly involved in the calculation of natural frequency. Worst case scenario in the term of transverse resonant vibration occurs when the natural frequency of lamella is equal to the vortex-shedding frequency. In this case

With advancement in technology, power requirements are reduced drastically for sensor nodes. The piezoelectric vibrationenergy harvesters generate sufficient power to low-powered sensor nodes. The main requirement of energy harvester is to provide a broad bandwidth. A conventional linear harvester does not satisfy this requirement. Therefore, the research focus is shifted to exploiting nonlinearity to widen the bandwidth of the harvester. Although nonlinear techniques are promising for broadening a bandwidth, reverse sweep shows reduced response as compared to the forward sweep. To overcome this issue, this thesis presents the design and development of a broadband piezoelectric vibrationenergy harvester based on a nonlinear multi-frequency compliant orthoplanar spring. This thesis is divided into three parts. The first part presents the design and experimental study of a tri-leg compliant orthoplanar spring for a broadband energy harvesting. The harvester performance is enhanced through the use of lightweight masses, which bring nonlinear vibration modes closer. The performance of the harvester is analyzed through development of a mathematical model based on the Duffing oscillator. The experimental and numerical results are in good agreement. The parametric study shows that an optimum performance is achieved by further reducing a gap in between the vibration modes using different weight masses. In the second part of the research, multiple (bi, quad and pent) leg compliant orthoplanar springs are designed to understand their role in expanding the bandwidth and reducing gap between vibration modes. The designed harvesters are compared by calculating the figure of merits. The quad-leg design provides a better performance in terms of power density and bandwidth among all the designs. The reverse sweep response is comparable to the forward sweep in terms of bandwidth. In the final part, a magnetic force is applied to the tri-leg harvester, which enhanced the voltage

The possibility of using solar-pumped lasers as solar energy converters is examined. The absorbing media considered are halogens or halogen compounds, which are dissociated to yield excited atoms, which then hand over energy to a molecular lasing medium. Estimates of the temperature effects for a Br2-CO2-He system with He as the cooling gas are given. High temperatures can cause the lower energy levels of the CO2 laser transition to be filled. The inverted populations are calculated and lasing should be possible. However, the efficiency is less than 0.001. Examination of other halogen-molecular lasant combinations (where the rate coefficients are known) indicate efficiencies in all cases of less than 0.005.

Approximately 4,000 vehicle bridges in the State of Minnesota contain structural timber members. Recent research at the University of Minnesota Duluth Natural Resources Research Institute (UMD NRRI) has been conducted on vibration testing of timber bridges as a means of developing rapid in-place testing techniques for assessing the structural health of bridges. The...

The vibrational response of finite periodic lattice structures subjected to periodic loading is investigated. Special attention is devoted to the response in frequency ranges with gaps in the band structure for the corresponding infinite periodic lattice. The effects of boundaries, viscous dampin...

Vibration harvesting is a promising concept to prolong the lifetime of batterypowered stand-alone systems, or even to enable their energy-autonomy. This thesis focuses on ambient vibrations converted by electromechanical transducers into electricity. The final goal is energy scavenging from train-induced vibrations in railway tunnels. This is achieved via the development of a suitable harvester for this environment and the practical demonstration of a vibrationpowered wireless sensor node (WSN). At the beginning of this thesis, extensive vibration measurements were performed in several traffic tunnels. The obtained unique data set formed the basis for the design and test of several harvesters. The railway sleeper was chosen as usable harvester location. A shock-resistant double-side suspended piezoelectric cantilever was developed. Several cantilevers with different eigenfrequencies are combined in an array, creating a robust harvester with a broad bandwidth. A field test of 7 days in the Loetschbergbasis-tunnel verified that, on average the sufficient energy for powering a virtual wireless sensor node was scavenged. For application in a real WSN, the harvester array was scaled up to 10 cantilevers. The power management for the sensor node was developed concurrently. The central component is a power switch that monitors the energy level in the system's storage capacitor and only triggers the wireless interface when sufficient energy is available. Combined with a train detection circuit, the presented energy-autonomous WSN reliably reports every passing vehicle. In addition to the development of an energy-autonomous fully integrated WSN, this work investigates nonlinear properties of PZT ceramics. Consideration of the elastostriction and the electrostriction enables a more precises prediction of the tip displacement of a piezoelectric cantilever actuator. Further, the elastostriction is exploited to modify the resonance frequency of a bimorph cantilever. Basing

Full Text Available Sinusoidal vibrations represent an ideal case. Technically, it is quite hard to generate pure sinusoidal vibrations without containing other spectral components, called harmonics. Sinusoidal vibrations can appear on propeller, propulsion and turbofan aircraft as well as on helicopters and aerospace structures. They can occur during different phases of flight (take-off, ascent, cruise, landing, etc.. The aim of this article is to present how a structure can be validated by using the mathematical formulas or a FEM software such as PATRAN-NASTRAN (and the equations behind it. As an application, an aerospace structure such as thruster brackets will be analyzed. A sinusoidal signal of 1g was applied on the attachment points and the response was read from the center of gravity of the thrusters.

Full Text Available The study investigated the role of excitation in energy harvesting applications. While the energy ultimately comes from the excitation, it was shown that the excitation may not always behave as a source. When the device characteristics do not perfectly match the excitation, the excitation alternately behaves as a source and a sink. The extent to which the excitation behaves as a sink determines the energy harvesting efficiency. Such contradictory roles were shown to be dictated by a generalized phase defined as the instantaneous phase angle between the velocity of the device and the excitation. An inductive prototype device with a diamagnetically levitated seismic mass was proposed to take advantage of the well established phase changing mechanism of vibro-impact to achieve a broader device bandwidth. Results suggest that the vibro-impact can generate an instantaneous, significant phase shift in response velocity that switches the role of the excitation. If introduced properly outside the resonance zone it could dramatically increase the energy harvesting efficiency.

Limitations of the static Woods–Saxon potential and the applicability of the energy dependent Woods–Saxon potential (EDWSP) model within the framework of one-dimensional Wong formula to explore the sub-barrier fusion data are highlighted. The inelastic surface excitations of the fusing nuclei are found to be ...

Abstract. Limitations of the static Woods–Saxon potential and the applicability of the energy- dependent Woods–Saxon potential (EDWSP) model within the framework of one-dimensional. Wong formula to explore the sub-barrier fusion data are highlighted. The inelastic surface exci- tations of the fusing nuclei are found to ...

This paper presents a non-resonant vibrationenergy harvester based on magnetoelectric transduction mechanism and mechanical frequency up-conversion using trampoline effect. The harvester utilizes a freely movable spherical permanent magnet which bounces off the aluminum springs integrated at both ends of the cavity, achieving frequency up-conversion from low frequency input vibration. Moreover, bonding method of magnetoelectric laminate composite has been optimized to provide higher strain to piezoelectric material and thus obtain a higher output voltage. A proof-of-concept energy harvesting device has been fabricated and tested. Maximum open-circuit voltage of 11.2V has been obtained and output power of 0.57μW has been achieved for a 50kΩ load, when the fabricated energy harvester was hand-shaken

This paper presents a non-resonant vibrationenergy harvester based on magnetoelectric transduction mechanism and mechanical frequency up-conversion using trampoline effect. The harvester utilizes a freely movable spherical permanent magnet which bounces off the aluminum springs integrated at both ends of the cavity, achieving frequency up-conversion from low frequency input vibration. Moreover, bonding method of magnetoelectric laminate composite has been optimized to provide higher strain to piezoelectric material and thus obtain a higher output voltage. A proof-of-concept energy harvesting device has been fabricated and tested. Maximum open-circuit voltage of 11.2V has been obtained and output power of 0.57μW has been achieved for a 50kΩ load, when the fabricated energy harvester was hand-shaken.

Many human activities induce excitations on ambient structures with various objects, causing the structures to vibrate. Accurate vibration excitation source detection and characterization enable human activity information inference, hence allowing human activity monitoring for various smart building applications. By utilizing structuralvibrations, we can achieve sparse and non-intrusive sensing, unlike pressure- and vision-based methods. Many approaches have been presented on vibration-based source characterization, and they often either focus on one excitation type or have limited performance due to the dispersion and attenuation effects of the structures. In this paper, we present our method to characterize two main types of excitations induced by human activities (impulse and slip-pulse) on multiple structures. By understanding the physical properties of waves and their propagation, the system can achieve accurate excitation tracking on different structures without large-scale labeled training data. Specifically, our algorithm takes properties of surface waves generated by impulse and of body waves generated by slip-pulse into account to handle the dispersion and attenuation effects when different types of excitations happen on various structures. We then evaluate the algorithm through multiple scenarios. Our method achieves up to a six times improvement in impulse localization accuracy and a three times improvement in slip-pulse trajectory length estimation compared to existing methods that do not take wave properties into account.

Energy harvesting technology is becoming increasingly important with the appearance of the Internet of things. In this study, a magnetostrictive clad steel plate for harvesting vibrationenergy was proposed. It comprises a cold-rolled FeCo alloy and cold-rolled steel joined together by thermal diffusion bonding. The performances of the magnetostrictive FeCo clad steel plate and conventional FeCo plate cantilevers were compared under bending vibration; the results indicated that the clad steel plate construct exhibits high voltage and power output compared to a single-plate construct. Finite element analysis of the cantilevers under bending provided insights into the magnetic features of a clad steel plate, which is crucial for its high performance. For comparison, the experimental results of a commercial piezoelectric bimorph cantilever were also reported. In addition, the cold-rolled FeCo and Ni alloys were joined by thermal diffusion bonding, which exhibited outstanding energy harvesting performance. The larger the plate volume, the more the energy generated. The results of this study indicated not only a promising application for the magnetostrictive FeCo clad steel plate as an efficient energy harvester, related to small vibrations, but also the notable feasibility for the formation of integrated units to support high-power trains, automobiles, and electric vehicles.

coefficient should be obtained in order to have a relatively small excitation on the cylinder. The drag coefficient can be controlled if the separation points of the boundary layers can be controlled. It is proposed to control the separation points by blowing compressed air out of the holes in the cylinder....... If the natura1 separation points of the boundary layers are rejected by blowing air out of the holes the drag coefficient will increase while it will decrease if it is possible to attach the boundary layer. The results from the experimental test have shown that it is possible to increase the drag coefficient...... with a factor 1.5-2 by blowing air out of the holes in a cylinder vibrating in a stationary water flow....

Quantum effects influence vibrational dynamics and energy flow in biomolecules, which play a central role in biomolecule function, including control of reaction kinetics. Lifetimes of many vibrational modes of proteins and their temperature dependence, as determined by quantum golden-rule-based calculations, exhibit trends consistent with experimental observation and distinct from estimates based on classical modeling. Particularly notable are quantum coherence effects that give rise to localization of vibrational states of sizable organic molecules in the gas phase. Even when such a molecule, for instance a cofactor, is embedded in a protein, remnants of quantum localization survive that influence vibrationalenergy flow and its dependence on temperature. We discuss these effects on the mode-damping rates of a cofactor embedded in a protein, using the green fluorescent protein chromophore as a specific example. We find that for cofactors of this size embedded in their protein and solvent environment at room temperature a golden-rule calculation often overestimates the mode-damping rate.

Vibrating wire sensors (VWS) are generally used for strain measurements of structures in buildings and civil infrastructures. In this paper, a wireless vibrating wire sensor node is developed which can measure resonance frequencies from vibrating wire sensors and can remotely communicate the frequencies by wireless. The wireless sensor node consists of a sensor module, which excites the vibrating wire and reads the resonance frequencies, a wireless communication module, which transmits the wire's resonance frequencies to the user or administrator, and a processor that controls the two modules. The wireless sensor node has the following characteristics: it has multiple channels to enable measurement of multiple vibrating wire sensors (up to four) using a single sensor node; it has a power-saving feature that enables operation for up to one year; and lastly, the wireless unit uses the 424 MHz UHF (ultra-high frequency) band with good diffraction that has an effect on minimizing the influence of impediments such as structural or nonstructural elements. The wireless sensor node is tested in terms of its measurement precision and its wireless communication performance. As a result, it is confirmed that the node enables the long-term structural health monitoring of buildings and infrastructures

This paper presents an analytical investigation of the fluidelastic coupling between an axial annular flow and a flexible vibrating axisymmetrical structure. The model presented is suited to single-phase, incompressible, viscous fluids and to annular flows of variable cross-section, axially symmetrical when the structure is motionless.An experimental validation of this model is presented at the end of the paper: the results obtained with the numerical model are compared with experimental data for an oscillating cylinder free to vibrate under the effect of a variable-cross-section annular flow. ((orig.))

An electromechanically coupled model for a cantilevered piezoelectric energy harvester with a proof mass is presented. Proof masses are essential in microscale devices to move device resonances towards optimal frequency points for harvesting. Such devices with proof masses have not been rigorously modeled previously; instead, lumped mass or concentrated point masses at arbitrary points on the beam have been used. Thus, this work focuses on the exact vibration analysis of cantilevered energy harvester devices including a tip proof mass. The model is based not only on a detailed modal analysis, but also on a thorough investigation of damping ratios that can significantly affect device performance. A model with multiple degrees of freedom is developed and then reduced to a single-mode model, yielding convenient closed-form normalized predictions of device performance. In order to verify the analytical model, experimental tests are undertaken on a macroscale, symmetric, bimorph, piezoelectric energy harvester with proof masses of different geometries. The model accurately captures all aspects of the measured response, including the location of peak-power operating points at resonance and anti-resonance, and trends such as the dependence of the maximal power harvested on the frequency. It is observed that even a small change in proof mass geometry results in a substantial change of device performance due not only to the frequency shift, but also to the effect on the strain distribution along the device length. Future work will include the optimal design of devices for various applications, and quantification of the importance of nonlinearities (structural and piezoelectric coupling) for device performance

In the present work, the experimental and theoretical vibrational spectra of 4-chlorobenzothioamide were investigated. The FT-IR (400-4000 cm-1) and μ-Raman spectra (100-4000 cm-1) of 4-chlorobenzothioamide in the solid phase were recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared and Raman intensities of the title molecule in the ground state were calculated using ab initio Hartree-Fock and density functional theory (B3LYP) methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and the theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 4-chlorobenzothioamide was also simulated to evaluate the effect of intermolecular hydrogen bonding on the vibrational frequencies. It was observed that the Nsbnd H stretching modes shifted to lower frequencies, while the in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular Nsbnd H&ctdot;S hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented.

In the present work, the experimental and theoretical vibrational spectra of 5-hydroxymethyluracil were investigated. The FT-IR (4000-400 cm-1) spectrum of the molecule in the solid phase was recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared intensities of the title molecule in the ground state were calculated using density functional B3LYP and M06-2X methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data, and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 5-hydroxymethyluracil molecule was also simulated to evaluate the effect of intermolecular hydrogen bonding on its vibrational frequencies. It was observed that the Nsbnd H stretching modes shifted to lower frequencies, while its in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular Nsbnd H&ctdot;O hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented.

Innovation in integrated circuit technology along with improved manufacturing processes has resulted in considerable reduction in power consumption of electromechanical devices. Majority of these devices are currently powered by batteries. However, the issues posed by batteries, including the need for frequent battery recharge/replacement has resulted in a compelling need for alternate energy to achieve self-sufficient device operation or to supplement battery power. Vibration based energy harvesting methods through piezoelectric transduction provides with a promising potential towards replacing or supplementing battery power source. However, current piezoelectric energy harvesters generate low specific power (power-to-weight ratio) when compared to batteries that the harvesters seek to replace or supplement. In this study, the potential of integrating lightweight cellular honeycomb structures with existing piezoelectric device configurations (bimorph) to achieve higher specific power is investigated. It is shown in this study that at low excitation frequency ranges, replacing the solid continuous substrate of a conventional piezoelectric bimorph with honeycomb structures of the same material results in a significant increase in power-to-weight ratio of the piezoelectric harvester. In order to maximize the electrical response of vibration based power harvesters, the natural frequency of these harvesters is designed to match the input driving frequency. The commonly used technique of adding a tip mass is employed to lower the natural frequency (to match driving frequency) of both, solid and honeycomb substrate bimorphs. At higher excitation frequency, the natural frequency of the traditional solid substrate bimorph can only be altered (to match driving frequency) through a change in global geometric design parameters, typically achieved by increasing the thickness of the harvester. As a result, the size of the harvester is increased and can be disadvantageous

Full Text Available Torsional vibration of shafts is a very important problem in engineering, in particular in ship engines and aeroengines. Due to their high levels of integration and complexity, it is hard to get their accurate structural data or accurate modal data. This lack of data is unhelpful to vibration control in the form of structural modifications. Besides, many parts in shaft systems are not allowed to be modified such as rotary inertia of a pump or an engine, which is designed for achieving certain functions. This paper presents a strategy for torsional vibration control of shaft systems in the form of structural modifications based on receptances, which does not need analytical or modal models of the systems under investigation. It only needs the torsional receptances of the system, which can be obtained by testing simple auxiliary structure attached to relevant locations of the shaft system and using the finite element model (FEM of the simple structure. An optimization problem is constructed to determine the required structural modifications, based on the actual requirements of modal frequencies and mode shapes. A numerical experiment is set up and the influence of several system parameters is analysed. Several scenarios of constraints in practice are considered. The numerical simulation results demonstrate the effectiveness of this method and its feasibility in solving torsional vibration problems in practice.

Graphical abstract: A system based on piezoelectric cymbals embedded in asphalt for the first time is used as harvester for wasted vibrationalenergy produced by traffic. Energy density in the range of other alternative sources is achieved, with an estimated projected cost that shows the feasibility of this harvesting energy system. - Highlights: • Piezoelectric cymbals have been directly integrated in asphalt for the first time. • Harvesting from wasted vibrationalenergy caused by vehicles is demonstrated to be feasible by this integration. • Energy density and cost are estimated to be competitive with other sources as photovoltaic. • A 10% of the energy generated in the Region of Madrid can be obtained by covering only the 0.6% of its roads. - Abstract: Piezoelectric cymbals with 29-mm diameter and different configurations are fabricated and tested to determine the best conditions to optimize the conversion of mechanical to electric energy. Then, the ones with the best results are integrated directly in asphalt to evaluate their performance as vibrationenergy harvesters in roads, in a test bench designed to characterize these parameters. The main cymbal parameters and their integration in the asphalt are determined. For the first time, the electrical energy that can be obtained with the embedment of cymbals in asphalt is evaluated. Each single piezoceramic cymbal recovers up to 16 μW for the pass of one heavy vehicle wheel. An extrapolation of the energy transformed by the integrated cymbals in roads with high vehicle densities, such as in a peri-urban motorway, is approached. Energy densities in the range of 40–50 MW h/m"2 can be obtained at 100 m of road (use of 30,000 cymbals), which could account for more than 65 MW h in a year. All this with a relatively low cost for an emerging technology (less than 2 €/kW h). The conversion of wasted and unused vibrationalenergy in roads by piezoelectric cymbals is thus proved as a real possibility of

Recent research into damage detection methodologies, embedded sensors, wireless data transmission and energy harvesting in aerospace environments has meant that autonomous structural health monitoring (SHM) systems are becoming a real possibility. The most promising system would utilise wireless sensor nodes that are able to make decisions on damage and communicate this wirelessly to a central base station. Although such a system shows great potential and both passive and active monitoring techniques exist for detecting damage in structures, powering such wireless sensors nodes poses a problem. Two such energy sources that could be harvested in abundance on an aircraft are vibration and thermal gradients. Piezoelectric transducers mounted to the surface of a structure can be utilised to generate power from a dynamic strain whilst thermoelectric generators (TEG) can be used to generate power from thermal gradients. This paper reports on the viability of these two energy sources for powering a wireless SHM system from vibrations ranging from 20 to 400Hz and thermal gradients up to 50°C. Investigations showed that using a single vibrationalenergy harvester raw power levels of up to 1mW could be generated. Further numerical modelling demonstrated that by optimising the position and orientation of the vibrational harvester greater levels of power could be achieved. However using commercial TEGs average power levels over a flight period between 5 to 30mW could be generated. Both of these energy harvesting techniques show a great potential in powering current wireless SHM systems where depending on the complexity the power requirements range from 1 to 180mW.

We study the gravitational dynamics of dark energy configurations. We report on the time evolution of the dark energy field configurations as well as the time evolution of the energy density to demonstrate the gravitational collapse of dark energy field configurations. We live in a Universe which is dominated by Dark Energy. According to current estimates about 75% of the Energy Density is in the form of Dark Energy. Thus when we consider gravitational dynamics and Structure Formation we expect Dark Energy to play an important role. The most promising candidate for dark energy is the energy density of fields in curved space-time. It therefore become a pressing need to understand the gravitational dynamics of dark energy field configurations. We develop and describe the formalism to study the gravitational collapse of fields given any general potential for the fields. We apply this formalism to models of dark energy motivated by particle physics considerations. We solve the resulting evolution equations which determine the time evolution of field configurations as well as the dynamics of space-time. Our results show that gravitational collapse of dark energy field configurations occurs and must be considered in any complete picture of our universe.

In this paper, a new design of a self-tuning bimorph PZT beam for maximum vibrationenergy harvesting is introduced. As is well known, a PZT beam harvester captures the most energy as it resonates with the ambient vibration. The ambient excitation frequency varies in nature so that proper tracking of the ambient frequency and adjusting the harvester’s resonance frequency accordingly would assure the most energy retrieved. The harvester introduced in the paper is composed of an elastic beam partially covered with two-sided PZT patches, the same as most others, but the method of tuning its resonance frequency is novel. A movable intermediate rigid support is attached to the beam and by adjusting the support’s position according to the sensed ambient frequency, the beam’s resonance frequency will coincide with the ambient frequency such that the harvested vibrationenergy is maximized. The theoretical analysis employs Hamilton’s principle, the assumed-mode method, and the receptance method. Numerical results are obtained and compared with the experimental ones. They show excellent agreement in a frequency versus support’s position chart. The most significant feature is that there can be up to ±35% of resonance frequency tunability. This achievement provides substantial advantages in power-harvesting applications. An experiment for base excitation to simulate the ambient vibration is setup as well and the results show that as little as 5% excitation frequency variation would cause more than 70% output voltage drop if there were no tuning ability. The novel design could significantly enhance the harvested energy in a short duration of time. (paper)

The Editor wishes to make the reader aware that the paper "A new method for predicting nonlinear structuralvibrations induced by ground impact loading" by Jun Liu, Yu Zhang, Bin Yun, Journal of Sound and Vibration, 331 (2012) 2129-2140, did not contain a direct citation of the fundamental and original work in this field by Dr. Mark Svinkin. The Editor regrets that this omission was not noted at the time that the above paper was accepted and published.

Both of atomic pair distribution function (PDF) and extended x-ray absorption fine structure (EXAFS) experiments have been carried out on unfilled and Yb-filled skutterudites Yb{sub x}Co{sub 4}Sb{sub 12} (x=0, 0.15, 0.2 and 0.25) samples. The structure refinements on PDF data confirm the large amplitude vibration of Yb atom and the dependence of Yb vibration amplitude on the filling content. Temperature dependent EXAFS experiment on filled skutterudites have been carried out at Yb L{sub Ⅲ}-edge in order to explore the local vibration behavior of filled atom. EXAFS experiments show that the Einstein temperature of the filled atom is very low (70.9 K) which agrees with the rattling behavior.

Structural health monitoring (SHM) is an engineering technique used to identify mechanical abnormalities not readily apparent through other means. Recently, SHM has been adapted for use in biological systems, but its invasive nature limits its clinical application. As such, the purpose of this pr......Structural health monitoring (SHM) is an engineering technique used to identify mechanical abnormalities not readily apparent through other means. Recently, SHM has been adapted for use in biological systems, but its invasive nature limits its clinical application. As such, the purpose...... of this project was to determine if a non-invasive form of SHM could identify structural alterations in the spines of living human subjects. Lumbar spines of 10 twin pairs were visualized by magnetic resonance imaging then assessed by a blinded radiologist to determine whether twin pairs were structurally...... concordant or discordant. Vibration was then applied to each subject's spine and the resulting response recorded from sensors overlying lumbar spinous processes. The peak frequency, area under the curve and the root mean square were computed from the frequency response function of each sensor. Statistical...

This study presents Nuclear Resonance Vibrational Spectroscopy (NRVS) data on the five-coordinate (5C) ferrous heme-nitrosyl complex [Fe(OEP)(NO)] (1, OEP(2-) = octaethylporphyrinato dianion) and the corresponding (15)N(18)O labeled complex. The obtained spectra identify two isotope sensitive features at 522 and 388 cm(-1), which shift to 508 and 381 cm(-1), respectively, upon isotope labeling. These features are assigned to the Fe-NO stretch nu(Fe-NO) and the in-plane Fe-N-O bending mode delta(ip)(Fe-N-O), the latter has been unambiguously assigned for the first time for 1. The obtained NRVS data were simulated using our quantum chemistry centered normal coordinate analysis (QCC-NCA). Since complex 1 can potentially exist in 12 different conformations involving the FeNO and peripheral ethyl orientations, extended density functional theory (DFT) calculations and QCC-NCA simulations were performed to determine how these conformations affect the NRVS properties of [Fe(OEP)NO]. These results show that the properties and force constants of the FeNO unit are hardly affected by the conformational changes involving the ethyl substituents. On the other hand, the NRVS-active porphyrin-based vibrations around 340-360, 300-320, and 250-270 cm(-1) are sensitive to the conformational changes. The spectroscopic changes observed in these regions are due to selective mechanical couplings of one component of E(u)-type (in ideal D(4h) symmetry) porphyrin-based vibrations with the in-plane Fe-N-O bending mode. This leads to the observed variations in Fe(OEP) core mode energies and NRVS intensities without affecting the properties of the FeNO unit. The QCC-NCA simulated NRVS spectra of 1 show excellent agreement with experiment, and indicate that conformer F is likely present in the samples of this complex investigated here. The observed porphyrin-based vibrations in the NRVS spectra of 1 are also assigned based on the QCC-NCA results. The obtained force constants of the Fe-NO and N

We have been developing small power generation device of capacitance-type to be converted to electrical energyvibrationenergy using an electret. In this Study, dielectric nanoparticles were mixed with an electret made of fluorocarbon polymer. As a result, implanted charge density of the electret was successfully enhanced thanks to the mixing of particles. A small sized vibrationenergy harvester (VEH) was fabricated using the fluorocarbon mixed with dielectric nano-particles. As a result of applying vibration (20 Hz, 0.65 G) to the fabricated VEH, The maximum generated power of approximately 50 μW was obtained

Vibrations and shocks are studied using various techniques and analyzed to predict their detrimental effect on the equipment and structures. In cases, where the effects of vibration become unacceptable, it may cause structural damage and affect the operation of the equipment. Hence, adding a discrete system to isolate the vibration from source becomes necessary. The Wire Rope Isolator (WRI) can be used to effectively isolate the system from disturbing vibrations. The WRI is a type of passive isolator that exhibits nonlinear behavior. It consists of stranded wire rope held between two metal retainer bars and the metal wire rope is made up of individual wire strands that are in frictional contact with each other, hence, it is a kind of friction-type isolator. This paper compiles the research work on wire rope isolators. This paper presents the research work under two categories, namely monotonic and cyclic loading behaviors of WRI. The review also discusses the different terminologies associated with vibration isolation system and highlights the comparison between various isolation systems. (paper)

The advent of very precise measurements of rate coefficients in reactions of muonium (Mu), the lightest hydrogen isotope, with H2 in its ground and first vibrational state and of kinetic isotope effects with respect to heavier isotopes has triggered a renewed interests in the field of muonic chemistry. The aim of the present article is to review the most recent results about the dynamics and mechanism of the reaction Mu+H2 to shed light on the importance of quantum effects such as tunnelling, the preservation of the zero point energy, and the vibrational adiabaticity. In addition to accurate quantum mechanical (QM) calculations, quasiclassical trajectories (QCT) have been run in order to check the reliability of this method for this isotopic variant. It has been found that the reaction with H2(v=0) is dominated by the high zero point energy (ZPE) of the products and that tunnelling is largely irrelevant. Accordingly, both QCT calculations that preserve the products' ZPE as well as those based on the Ring Polymer Molecular Dynamics methodology can reproduce the QM rate coefficients. However, when the hydrogen molecule is vibrationally excited, QCT calculations fail completely in the prediction of the huge vibrational enhancement of the reactivity. This failure is attributed to tunnelling, which plays a decisive role breaking the vibrational adiabaticity when v=1. By means of the analysis of the results, it can be concluded that the tunnelling takes place through the ν1=1 collinear barrier. Somehow, the tunnelling that is missing in the Mu+H2(v=0) reaction is found in Mu+H2(v=1).

The combination of nonlinear bistable and flextensional mechanisms has the advantages of wide operating frequency and high equivalent piezoelectric constant. In this paper, three magnetically coupled flextensional vibrationenergy harvesters (MF-VEHs) are designed from three magnetically coupled vibration systems which utilize a magnetic repulsion, two symmetrical magnetic attractions and multi-magnetic repulsions, respectively. The coupled dynamic models are developed to describe the electromechanical transitions. Simulations under harmonic excitation and random excitation are carried out to investigate the performance of the MF-VEHs with different parameters. Experimental validations of the MF-VEHs are performed under different excitation levels. The experimental results verify that the developed mathematical models can be used to accurately characterize the MF-VEHs for various magnetic coupling modes. A comparison of three MF-VEHs is provided and the results illustrate that a reasonable arrangement of multiple magnets can reduce the threshold excitation intensity and increase the harvested energy.

In hydrothermal condition hafnium selenite with estimated chemical composition Hf(SeO3)2·n(H2O) was obtained and characterized by powder X-Ray diffraction, IR spectroscopy and thermogravimetrical analysis. The composition of the obtained crystalline phase was established as dihydrate of tetraaqua complex of the hafnium selenite [Hf(SeO3)2(H2O)4]·2H2O. The results of the thermogravimetrical analysis are shown that the two hydrated water molecules are released in the temperature interval 80-110°C, while the four coordinated water molecules - at 210-300°C. By DFT method, with Becke's three parameter exchange-functional combined with gradient-corrected correlation functional of Lee, Yang and Parr and 6-31G(d), 6-311 + G(d,p) basis sets and LANL2DZ for Hf atom were calculated the molecular structure, vibrational frequencies and thermodynamic properties of the structure. The UV-Vis spectra and electronic properties are presented. The energy and oscillator strength calculated by time-dependent density functional theory corresponds well with the experimental ones. Molecular electrostatic potential (MEP) was performed. Mulliken population analysis on atomic charges was also calculated. The stability and intramolecular interactions are interpreted by NBO analysis.

a multitude of different sprung masses each strongly resisting any motion of the main structure (master) at their base antiresonance. The “theory of structural fuzzy” is intended for modeling such high damping. In the present article the theory of fuzzy structures is briefly outlined and a method of modeling...

Nonlinear behavior is the ordinary feature of the vast majority of dynamical systems and noise is commonly present in any finite temperature physical and chemical system. In this article we briefly review the potentially beneficial outcome of the interplay of noise and nonlinearity by addressing the novel field of vibrationenergy harvesting. The role of nonlinearity in a piezoelectric harvester oscillator dynamics is modeled with nonlinear stochastic differential equation.

comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE...µm in order to facilitate the flow diagnostics. The center jet flow issues through a CNC- machined stainless nozzle, which can be replaced to provide...the mixing in the shear layer, which will be used to compare with the relaxation time of the vibrationalenergy, was defined as the eddy turnover time

In the high intensity proton accelerator as the Japan Proton Accelerator Research Complex (J-PARC) accelerators, serious radiation and residual dose is induced by a small beam loss such a beam halo. Therefore, diagnostics of the beam halo formation is one of the most important issues to control the beam loss. For the beam halo monitor, the vibration wire monitor (VWM) has a potential for investigating the beam halo and weak beam scanning. The VWM has a wide dynamic range, high resolution and the VWM is not susceptible to secondary electrons and electric noises. We have studied the VWM features as a new beam-halo monitor on the test stand with low energy electron gun. The frequency shift of the irradiated vibration wire was confirmed about wire material and the electron beam profile measured by using the VWM was consistent with the results of the Faraday cup measurement. Also we calculated a temperature distribution on the vibration wire which is irradiated by the electron beam with the numerical simulation. The simulations have been fairly successful in reproducing the transient of the irradiated vibration wire frequency measured by test stand experiments. In this paper, we will report a result of performance evaluation for the VWM on the test stands and discuss the VWM for beam halo diagnostic. (author)

The effects of 15 solvents on the C=O stretching vibrational frequency of flurbiprofen (FBF) were determined to investigate solvent-solute interactions. Solvent effects on the geometry and C=O stretching vibrational frequency, ν(C=O), of FBF were studied theoretically at the DFT/B3LYP and HF level in combination with the polarizable continuum model and experimentally using attenuated total reflection infrared spectroscopy (ATR-IR). The calculated C=O stretching frequencies in the liquid phase are in agreement with experimental values. Moreover, the wavenumbers of ν(C=O) of FBF in different solvents have been obtained and correlated with the Kirkwood-Bauer-Magat equation (KBM), the solvent acceptor numbers (ANs), and the linear solvation energy relationships (LSERs). The solvent-induced stretching vibrational frequency shifts displayed a better correlation with the LSERs than with the ANs and KBM.

Large eddy simulation is used to explore flow features and energy exchange physics between turbulent flow and structurevibration in the near-wall region with fluid-structure interaction (FSI). The statistical turbulence characteristics in the near-wall region of a vibrating wall, such as the skin frictional coefficient, velocity, pressure, vortices, and the coherent structures have been studied for an aerofoil blade passage of a true three-dimensional hydroturbine. The results show that (i) FSI greatly strengthens the turbulence in the inner region of y+ < 25; and (ii) the energy exchange mechanism between the flow and the vibration depends strongly on the vibration-induced vorticity in the inner region. The structuralvibration provokes a frequent action between the low- and high-speed streaks to balance the energy deficit caused by the vibration. The velocity profile in the inner layer near the vibrating wall has a significant distinctness, and the viscosity effect of the fluid in the inner region decreases due to the vibration. The flow features in the inner layer are altered by a suitable wall vibration.

Vibrationenergy harvesting has been extensively studied in recent years to explore a continuous power source for sensor networks and low-power electronics. Torsional vibration widely exists in mechanical engineering; however, it has not yet been well exploited for energy harvesting. This paper presents a theoretical model and an experimental validation of a torsional vibrationenergy harvesting system comprised of a shaft and a shear mode piezoelectric transducer. The piezoelectric transducer position on the surface of the shaft is parameterized by two variables that are optimized to obtain the maximum power output. The piezoelectric transducer can work in d 15 mode (pure shear mode), coupled mode of d 31 and d 33, and coupled mode of d 33, d 31 and d 15, respectively, when attached at different angles. Approximate expressions of voltage and power are derived from the theoretical model, which gave predictions in good agreement with analytical solutions. Physical interpretations on the implicit relationship between the power output and the position parameters of the piezoelectric transducer is given based on the derived approximate expression. The optimal position and angle of the piezoelectric transducer is determined, in which case, the transducer works in the coupled mode of d 15, d 31 and d 33.

Self-powered systems have become the need of the hour and several devices and techniques were proposed in favour of this crisis. Among the various sources, vibrations, being the most practical scenario, is chosen in the present study to investigate for the possibility of harvesting energy. Various methods were devised to trap the energy generated by vibrating bodies, which would otherwise be wasted. One such concept is termed as flow-induced vibration which involves the flow of a fluid across a bluff body that oscillates due to a phenomenon known as vortex shedding. These oscillations can be converted into electrical energy by the use of piezoelectric patches. A two degree of freedom system containing a cylinder as the primary mass and a cantilever beam as the secondary mass attached with a piezoelectric circuit, was considered to model the problem. Three wake oscillator models were studied in order to determine the one which can generate results with high accuracy. It was found that Facchinetti model produced better results than the other two and hence a parametric study was performed to determine the favourable range of the controllable variables of the system. A fitness function was formulated and optimization of the selected parameters was done using genetic algorithm. The parametric optimization led to a considerable improvement in the harvested voltage from the system owing to the high displacement of secondary mass.

This article presents a non-resonant magneto-mechanical vibrationenergy harvester. When externally excited, the energy harvester converts vibrations into electric charge using a guided levitated magnet oscillating inside a multi-turn coil that is fixed around the exterior of the energy harvester. The levitated magnet is guided using four oblique mechanical springs. A prototype of the energy harvester is fabricated using additive manufacturing. Both experiment and model are used to characterize the static and dynamic behavior of the energy harvester. Measured restoring forces show that the fabricated energy harvester retains a mono-stable potential energy well with desired stiffness nonlinearities. Results show that magnetic spring results in hardening effect which increases the resonant frequency of the energy harvester. Additionally, oblique mechanical springs introduce geometric, negative, nonlinear stiffness which improves the harvester's response towards lower frequency spectrum. The unique design can produce a tunable energy harvester with multi-well potential energy characteristics. A finite element model is developed to estimate the average radial flux density experienced by the multi-turn coil. Also, a lumped parameter model of the energy harvester is developed and validated against measured data. Both upward and downward frequency sweeps are performed to determine the frequency response of the harvester. Results show that at higher excitation levels hardening effects become more apparent, and the system dynamic response turns into non-resonant. Frequency response curves exhibit frequency jump phenomena as a result of coexistence of multiple energy states at the frequency branch. The fabricated energy harvester is hand-held and measures approximately 100.5 [cm3] total volume. For a base excitation of 1.0 g [m/s2], the prototype generates a peak voltage and normalized power density of approximately 3.5 [V] and 0.133 [mW/cm3 g2], respectively, at 15.5 [Hz].

Full Text Available This paper presents a restoration solution of increased vibration of the fan plant's support structure. Based on vibrodiagnostic tests and dynamic analysis, a technical solution of the problem is given with additional steel bracing. There is particular emphasis on the diagnosis and forming of a dynamic model.

Full Text Available In this paper we present an experimental study of a three dimensional physical model of a three-floor structure subjected to forced vibrations by imposing displacements in its support. The aim of this work is to analyze the behavior of the building when a dynamic vibration absorber (DVA is acting. An analytic simplified analysis and a numerical study are developed to obtain the natural frequencies of the structure. Experiments are carried out in a vibrating table. The frequency range to be experimentally analyzed is determined by the first natural frequency of the structure for which the DVA damping effects are verified. The equipment capabilities, i.e. the frequencies, amplitudes and admissible load, limit the analyses. Nevertheless, satisfactory results are obtained for the study of the first mode of vibration. The effect of different amplitudes of the imposed support motion is also analyzed. In addition, the damping effect of the DVA device is evaluated upon varying its mass and its location in the structure. The characteristic curves in the frequency domain are obtained computing the Fast Fourier Transformation (FFT of the acceleration history registered with piezoelectric accelerometers at different checkpoints for the cases analyzed.

A number of researchers have been focused on structuralvibration control in the past three decades over the world and fruit achievements have been made. This paper introduces the recent advances in structuralvibration control including passive, active and semiactive control in mainland China. Additionally, the co-author extends the structuralvibration control to failure mode control. The research on the failure mode control is also involved in this paper. For passive control, this paper introduces full scale tests of buckling-restrained braces conducted to investigate the performance of the dampers and the second-editor of the Code of Seismic Design for Buildings. For active control, this paper introduces the HMD system for wind-induced vibration control of the Guangzhou TV tower. For semiactive control, the smart damping devices, algorithms for semi-active control, design methods and applications of semi-active control for structures are introduced in this paper. The failure mode control for bridges is also introduced

The internal structures of pressurized water reactors are the seat of vibrations induced by fluctuations in primary fluid flow. A knowledge of these phenomena is indispensable in order to ensure that the structures are in proper mechanical order. It can also be used for operational monitoring. This paper describes all the methods developed and the results already achieved in this domain. The first part deals with tests on mockup associated with the calculation models which afforded a good knowledge of the vibrational characteristics of the internal structures, as well as the measurements made during hot tests of certain reactors which made it possible to qualify these models on real structures. The second part describes the means of detection (neutron noise, external accelerometers) as well as the processing methods used in the follow-up. A few typical results obtained on site are then presented. Finally, the general principles of operational monitoring of the mechanical behavior of the internal structures are described [fr

Structures with high concentration of mass at or close to the top such as highway bridge piers are vulnerable in earthquakes or accidents. In this paper, a simple and convenient retrofit strategy is proposed for minimizing vibrations and damages, extending service life and preventing collapse of existing structures. The proposed system comprises of tension-only cables secured to the sides of the structure through gravity anchor blocks that are free to move in vertical shafts. The system is installed in such a way that the cables do not induce unnecessary stress on the main structure when there is no lateral motion or vibration. The effectiveness of controlling global structural responses is investigated for tension-only bilinear-elastic behaviour of cables. Results of a realistic case study for a reinforced concrete bridge pier show that response reduction is remarkably well under seismic excitation.

Transforming energy use in cities to address the threats of climate change and resource scarcity is a major challenge in urban development. This study takes stock of the state of energy in urban policy and planning and reveals potentials of and constraints to energy-efficient urban development....... The relationship between energy and urban structure provides a framework for discussing the role of urban planning to increase energy efficiency in cities by means of three in-depth case studies of medium-sized cities in Northern Europe: Eskilstuna in Sweden, Turku in Finland and Tartu in Estonia. In some ways...... these cities go ahead when it comes to their national climate and energy policies and aim to establish urban planning as an instrument to regulate and influence the city’s transition in a sustainable way. At the same time, the cities are constantly facing goal conflicts and limitations to their scope of action...

To verify the beam-type and oval-type vibratory characteristics of a spherical shell structure, two test specimens were made and vibration tests were carried out. Results of these tests are compared with results of detailed analyses using 3-D FEM and 2-D axisymmetric FEM models. The analytical results of overall vibratory characteristics are in good agreement with the test results, has been found that the effect of the attached mass should be considered in evaluating local vibration. The replacing method into equivalent beam model is proposed

Control Moment Gyroscopes (CMGs) are used for non-propulsive attitude control of satellites and space stations, including the International Space Station (ISS). CMGs could be essential for future long duration space missions due to the fact that they help to save propellant. CMGs were successfully tested on the ground for many years, and have been successfully used on satellites. However, operations have shown that the CMG service life on the ISS is significantly shorter than predicted. Since the dynamic environment of the ISS differs greatly from the nominal environment of satellites, it was important to analyze how operations specific to the station (dockings and undockings, huge solar array motion, crew exercising, robotic operations, etc) can affect the CMG performance. This task became even more important since the first CMG failure onboard the ISS. The CMG failure resulted in the limitation of the attitude control capabilities, more propellant consumption, and additional operational issues. Therefore, the goal of this work was to find out how the vibrations of a space vehicle structure, caused by a variety of onboard operations, can affect the CMG dynamics and performance. The equations of CMG motion were derived and analyzed for the case when the gyro foundation can vibrate in any direction. The analysis was performed for unbalanced CMG gimbals to match the CMG configuration on ISS. The analysis showed that vehicle structurevibrations can amplify and significantly change the CMG motion if the gyro gimbals are unbalanced in flight. The resonance frequencies were found. It was shown that the resonance effect depends on the magnitude of gimbal imbalance, on the direction of a structurevibration, and on gimbal bearing friction. Computer modeling results of CMG dynamics affected by the external vibration are presented. The results can explain some of the CMG vibration telemetry observed on ISS. This work shows that balancing the CMG gimbals decreases the effect

Full Text Available This paper deals with the study of algorithms for robust active vibration control in flexible structures considering uncertainties in system parameters. It became an area of enormous interest, mainly due to the countless demands of optimal performance in mechanical systems as aircraft, aerospace, and automotive structures. An important and difficult problem for designing active vibration control is to get a representative dynamic model. Generally, this model can be obtained using finite element method (FEM or an identification method using experimental data. Actuators and sensors may affect the dynamics properties of the structure, for instance, electromechanical coupling of piezoelectric material must be considered in FEM formulation for flexible and lightly damping structure. The nonlinearities and uncertainties involved in these structures make it a difficult task, mainly for complex structures as spatial truss structures. On the other hand, by using an identification method, it is possible to obtain the dynamic model represented through a state space realization considering this coupling. This paper proposes an experimental methodology for vibration control in a 3D truss structure using PZT wafer stacks and a robust control algorithm solved by linear matrix inequalities.

This benchmark exercise is the continuation of the state-of-the-art review (EUR 11369 EN) which concluded that the random vibration approach could be an effective tool in seismic analysis of nuclear power plants, with potential advantages on time history and response spectrum techniques. As compared to the latter, the random vibration method provides an accurate treatment of multisupport excitations, non classical damping as well as the combination of high-frequency modal components. With respect to the former, the random vibration method offers direct information on statistical variability (probability distribution) and cheaper computations. The disadvantages of the random vibration method are that it is based on stationary results, and requires a power spectral density input instead of a response spectrum. A benchmark exercise to compare the three methods from the various aspects mentioned above, on one or several simple structures has been made. The following aspects have been covered with the simplest possible models: (i) statistical variability, (ii) multisupport excitation, (iii) non-classical damping. The random vibration method is therefore concluded to be a reliable method of analysis. Its use is recommended, particularly for preliminary design, owing to its computational advantage on multiple time history analysis

Periodic plane-wave density functional theory (DFT) and molecular cluster hybrid molecular orbital-DFT (MO-DFT) calculations were performed on models of phosphate surface complexes on the (100), (010), (001), (101), and (210) surfaces of α-FeOOH (goethite). Binding energies of monodentate and bidentate HPO(4)(2-) surface complexes were compared to H(2)PO(4)(-) outer-sphere complexes. Both the average potential energies from DFT molecular dynamics (DFT-MD) simulations and energy minimizations were used to estimate adsorption energies for each configuration. Molecular clusters were extracted from the energy-minimized structures of the periodic systems and subjected to energy reminimization and frequency analysis with MO-DFT. The modeled P-O and P---Fe distances were consistent with EXAFS data for the arsenate oxyanion that is an analog of phosphate, and the interatomic distances predicted by the clusters were similar to those of the periodic models. Calculated vibrational frequencies from these clusters were then correlated with observed infrared bands. Configurations that resulted in favorable adsorption energies were also found to produce theoretical vibrational frequencies that correlated well with experiment. The relative stability of monodentate versus bidentate configurations was a function of the goethite surface under consideration. Overall, our results show that phosphate adsorption onto goethite occurs as a variety of surface complexes depending on the habit of the mineral (i.e., surfaces present) and solution pH. Previous IR spectroscopic studies may have been difficult to interpret because the observed spectra averaged the structural properties of three or more configurations on any given sample with multiple surfaces.

Full Text Available This paper presents a wireless sensor node (WSN system where an electromagnetic (EM energy harvester is utilized for charging its rechargeable batteries while the system is operational. The capability and the performance of an in-house low-frequency EM energy harvester for charging rechargeable NiMH batteries were experimentally verified in comparison to a regular battery charger. Furthermore, the power consumption of MicaZ motes, used as the WSN, was evaluated in detail for different operation conditions. The battery voltage and current were experimentally monitored during the operation of the MicaZ sensor node equipped with the EM vibrationenergy harvester. A compact (24.5 cm3 in-house EM energy harvester provides approximately 65 µA charging current to the batteries when excited by 0.4 g acceleration at 7.4 Hz. It has been shown that the current demand of the MicaZ mote can be compensated for by the energy harvester for a specific low-power operation scenario, with more than a 10-fold increase in the battery lifetime. The presented results demonstrate the autonomous operation of the WSN, with the utilization of a vibration-based energy harvester.

This paper studies energy harvesting from heartbeat vibrations for powering leadless pacemakers. Unlike traditional pacemakers, leadless pacemakers are implanted inside the heart and the pacemaker is in direct contact with the myocardium. A leadless pacemaker is in the shape of a cylinder. Thus, in order to utilize the available 3-dimensional space for the energy harvester, we choose a fan-folded 3D energy harvester. The proposed device consists of several piezoelectric beams stacked on top of each other. The volume of the energy harvester is 1 cm3 and its dimensions are 2 cm × 0.5 cm × 1 cm. Although high natural frequency is generally a major concern with micro-scale energy harvesters, by utilizing the fan-folded geometry and adding tip mass and link mass to the configuration, we reduced the natural frequency to the desired range. This fan-folded design makes it possible to generate more than 10 μ W of power per cubic centimeter. The proposed device is compatible with Magnetic Resonance Imaging. Although the proposed device is a linear energy harvester, it is relatively insensitive to the heart rate. The natural frequencies and the mode shapes of the device are calculated analytically. The accuracy of the analytical model is verified by experimental investigations. We use a closed loop shaker system to precisely replicate heartbeat vibrations in vitro.

Full Text Available There is increasing recognition about the importance of enhancing energy expenditure (EE for weight control through increases in low-intensity physical activities comparable with daily life (1.5-4 METS. Whole-body vibration (WBV increases EE modestly and could present both a useful adjuvant for obesity management and tool for metabolic phenotyping. However, it is unclear whether a "dose-response" exists between commonly-used vibration frequencies (VF and EE, nor if WBV influences respiratory quotient (RQ, and hence substrate oxidation. We aimed to investigate the EE-VF and RQ-VF relationships across three different frequencies (30, 40, and 50Hz.EE and RQ were measured in 8 healthy young adults by indirect calorimetry at rest, and subsequently during side-alternating WBV at one of 3 VFs (30, 40, and 50 Hz. Each frequency was assessed over 5 cycles of intermittent WBV (30s vibration/30s rest, separated by 5 min seated rest. During the WBV participants stood on the platform with knees flexed sufficiently to maintain comfort, prevent transmission of vibration to the upper body, and minimise voluntary physical exertion. Repeatability was assessed across 3 separate days in a subset of 4 individuals. In order to assess any sequence/habituation effect, an additional group of 6 men underwent 5 cycles of intermittent WBV (30s vibration/30s rest at 40 Hz, separated by 5 min seated rest.Side-alternating WBV increased EE relative to standing, non-vibration levels (+36%, p<0.001. However, no differences in EE were observed across VFs. Similarly, no effect of VF on RQ was found, nor did WBV alter RQ relative to standing without vibration.No relationship could be demonstrated between EE and VF in the range of 30-50Hz, and substrate oxidation did not change in response to WBV. Furthermore, the thermogenic effect of intermittent WBV, whilst robust, was quantitatively small (<2 METS.

The vibrational coarse structure and the band shapes of electronic absorption spectra are often dominated by just a few molecular vibrations. By contrast, the simulation of the vibronic structure even in the simplest theoretical models usually requires the calculation of the entire set of normal modes of vibration. Here, we exploit the idea of the mode-tracking protocol [M. Reiher and J. Neugebauer, J. Chem. Phys. 118, 1634 (2003)] in order to directly target and selectively calculate those normal modes which have the largest effect on the vibronic band shape for a certain electronic excitation. This is achieved by defining a criterion for the importance of a normal mode to the vibrational progressions in the absorption band within the so-called “independent mode, displaced harmonic oscillator” (IMDHO) model. We use this approach for a vibronic-structure investigation for several small test molecules as well as for a comparison of the vibronic absorption spectra of a truncated chlorophyll a model and the full chlorophyll a molecule. We show that the method allows to go beyond the often-used strategy to simulate absorption spectra based on broadened vertical excitation peaks with just a minimum of computational effort, which in case of chlorophyll a corresponds to about 10% of the cost for a full simulation within the IMDHO approach.

In this paper a new class of shunted electromagnetic damping treatment is proposed: a non-contact electromagnetic shunt damper (NC-EMSD). The NC-EMSD consists of an electromagnet attached to a host structure, a permanent magnet attached to the fixed boundary and an electrical impedance connected to the terminals of the electromagnet. The electromagnet and the shunt impedance constitute a closed circuit. When the structurevibrates, an induced electromotive force will be produced and results in the electromagnetic force as damping force, which can suppress the vibration of the structure. The model of NC-EMSD is built up based on the equivalent current method. The governing equations of the beam with NC-EMSD are established using Hamilton's principle. The capacitor-matching-inductance (CMI) method and the negative resistive capacitor-matching-inductance (NR-CMI) method are proposed, respectively. Then the vibration control of a cantilever beam with NC-EMSD is simulated and measured by CMI and NR-CMI control methods, respectively. The results show that both the CMI and NR-CMI can attenuate the vibration effectively, and the NR-CMI provides much better control performance than that by CMI. It is indicated as well from the studies that the decrease of either the gap between the magnet pair or the resistance of the shunt impedance contributes to the improvement of control performance

Full Text Available The free vibration of frame structures has been usually studied in literature without considering the effect of axial loads. In this paper, the continuous system method is employed to investigate this effect on the free flexural and torsional vibration of two and three dimensional symmetric frames. In the continuous system method, in approximate analysis of buildings, commonly, the structure is replaced by an equivalent beam which matches the dominant characteristics of the structure. Accordingly, the natural frequencies of the symmetric frame structures are obtained through solving the governing differential equation of the equivalent beam whose stiffness and mass are supposed to be uniformly distributed along the length. The corresponding axial load applied to the replaced beam is calculated based on the total weight and the number of stories of the building. A numerical example is presented to show the simplicity and efficiency of the proposed solution.

The new hydrogen bonded molecular complex 1,2,4-triazolium hydrogenselenate (THS) is prepared by the reaction of 1H-1,2,4-triazole and selenic acid. This complex is stabilised by N-H&ctdot;O and C-H&ctdot;O hydrogen bonding and electrostatic attractive forces between 1H and 1,2,4-triazolium cations and hydrogen selenate anions. The XRD studies revealed that intermolecular proton transfer occur from selenic acid to 1H-1,2,4-triazole molecule, results in the formation of 1,2,4-triazolium hydrogenselenate which contains 1,2,4-triazolium cations and hydrogenselenate anions. The molecular structure of THS crystal has also been optimised by using Density Functional Theory (DFT) using B3LYP/cc-pVTZ and B3LYP/6-311++G** methods in order to find the whole characteristics of the molecular complex. The theoretical structural parameters such as bond length, bond angle and dihedral angle determined by DFT methods are well agreed with the XRD parameters. The atomic charges and thermodynamic properties are also calculated and analysed. The energies of frontier molecular orbitals HOMO, LUMO, HOMO-1, LUMO+1 and LUMO-HUMO energy gap are calculated to understand the kinetic stability and chemical reactivity of the molecular complex. The natural bond orbital analysis (NBO) has been performed in order to study the intramolecular bonding interactions and delocalisation of electrons. These intra molecular charge transfer may induce biological activities such as antimicrobials, antiinflammatory, antifungal etc. The complete vibrational assignments of THS have been performed by using FT-IR and FT-Raman spectra.

chemical density functional theory (DFT) calculation. ... Recently, much attention has been devoted to the large family of organic–inorganic metal halides due to their partic- ular structural features and physical properties. ... Integration.

Full Text Available In order to study the vibration problem of liquid-solid coupling of rectangular liquid-storage structure with horizontal elastic baffle, ignoring the influence of surface gravity wave, two different velocity potential functions corresponding to the liquid above and below the elastic baffle are assumed; based on the theory of mathematical equation and energy method, the formulas of basic frequency of liquid-solid coupling vibration system are derived, the baffle joined to the tank wall with 3 kinds of boundary conditions, namely, four edges simply supported, two opposite edges clamped and two opposite edges simply supported, and four edges clamped; the influence rules of baffle length-width ratio, the ratio of baffle height to liquid level, baffle elastic modulus, baffle density, baffle thickness, and liquid density on the coupling vibration performance are studied. The results show that the frequency of the clamped boundary is minimum; the influences of baffle length-width ratio and relative height on the basic frequency are much greater than that of the other system parameters; the relation between baffle length-width ratio and the frequency is exponential, while baffle relative height has a parabola relation with the frequency; the larger the baffle length-width ratio, the closer the baffle to the liquid level; the coupling frequency will be reduced more obviously.

In today's cutting costs environment in the offshore wind industry, significant achievements can be made with a better assessment of dynamic soil-pile interaction. Of the main damping mechanisms active at an OWT (offshore wind turbine), least is known about soil damping. The values for this contribution used in the industry today - mostly calculated analogously to a study performed in 1980 - are expected to be on the low side. More research on the topic is recommended. Presence of more damping than currently assumed, would signify that the (often) design driving fatigue damage accumulation is lower than assumed. This would justify designing more light-weight structures using less construction steel, or allowing for longer (insured) OWT lifetimes then the now applied 20 years. Both these measures significantly decrease costs of offshore wind. This paper evaluates measured signals of twelve 'rotorstop' - test on an OWT at Dong Energy owned - Burbo Banks windfarm. The vibration decay was measured with an accelerometer and strain gauges along the tower. A simplistic analytical model has been developed enabling analyses of the measured signals. Two main modal shapes were identified with similar shape, but deviating amplitudes in the soil profile. The large difference in damping that exists between the vibrations of these modes is attributed to the difference in influence that the soil can have on these vibrations. The found effect of soil on the damping of this particular OWT is significantly larger than the order of magnitude used in the industry today.

Power source has become a serious restriction of wireless sensor network. High efficiency, self-energized and long-life renewable source is the optimum solution for unmanned sensor network applications. However, single renewable power source can be easily affected by ambient environment, which influences stability of the system. In this work, a hybrid power system consists of a solar panel, a vibrationenergy harvester and a lithium battery is demonstrated. The system is able to harvest multiple types of ambient energy, which extends its applicability and feasibility. Experiments have been conducted to verify performance of the system.

We present a microelectromechanical system (MEMS) based PZT/PZT thick film bimorph vibrationenergy harvester with an integrated silicon proof mass. Most piezoelectric energy harvesting devices use a cantilever beam of a non piezoelectric material as support beneath or in-between the piezoelectric...... elements. We show experimental results from two types PZT/PZT harvesting devices, one where the Pb(ZrxTi1−x)O3 (PZT) thick films are high pressure treated during the fabrication and the other where the treatment is omitted. We find that with the high pressure treatment prior to PZT sintering, the films...

In order to improve the prediction of wear problems due to flow-induced vibration in PWR components, an inverse method for identifying a distributed random excitation acting on a dynamical system has been developed at EDF. This method, whose applications go far beyond the flow-induced vibration field, has been implemented into the MEIDEE software. This method is presented. (author)

.... This theory answered the Navy's need for rapid and cost-effective testing by the guiding the construction of emulators, which are electro-mechanical models that approximate the input-output energy flow between machinery and the foundation on which it is mounted.

Passive liquid dampers have been used to effectively reduce the dynamic response of civil infrastructures subjected to earthquakes or strong winds. The design of liquid dampers for structuralvibration control involves the determination of the optimal parameters. This paper presents an optimal design methodology for tuned liquid column dampers (TLCDs) based on the H∞ control theory. A practical structure, Dalian Xinghai Financial Business Building, is used to illustrate the feasibility of the...

An ab initio study of the stability, structural, electronic. and optical properties has been performed for 46 zinc sulfide nanoclusters Zn x S y (x + y = n = 2 to 5). Five out of them are seen to be unstable as their vibrational frequencies are found to be imaginary. A B3LYP-DFT/6-311G(3df) method is employed to optimize the geometries and a TDDFT method is used for the study of the optical properties. The binding energies (BE), HOMO-LUMO gaps and the bond lengths have been obtained for all the clusters. For the ZnS 2 , ZnS 3 , and ZnS 4 nanoclusters, our stable structures are seen to be different from those obtained earlier by using the effective core potentials. We have also considered the zero point energy (ZPE) corrections ignored by the earlier workers. For a fixed value of n, we designate the most stable structure the one, which has maximum final binding energy per atom. The adiabatic and vertical ionization potentials (IP) and electron affinities (EA), charges on the atoms, dipole moments, optical properties, vibrational frequencies, infrared intensities, relative infrared intensities, and Raman scattering activities have been investigated for the most stable structures. The nanoclusters containing large number of S atoms for each n is found to be most stable. The HOMO-LUMO gap decreases from n = 2-3 and then increases above n = 3. The IP and EA both fluctuate with the cluster size n. The optical absorption is quite weak in visible region but strong in the ultraviolet region in most of the nanoclusters except a few. The optical absorption spectrum or electron energy loss spectrum (EELS) is unique for every nanocluster and may be used to characterize a specific nanocluster. The growth of most stable nanoclusters may be possible in the experiments.

We report cross sections for electron-impact excitation of vibrational quanta in furfural, at intermediate incident electron energies (20, 30, and 40 eV). The present differential cross sections are measured over the scattered electron angular range 10°-90°, with corresponding integral cross sections subsequently being determined. Furfural is a viable plant-derived alternative to petrochemicals, being produced via low-temperature plasma treatment of biomass. Current yields, however, need to be significantly improved, possibly through modelling, with the present cross sections being an important component of such simulations. To the best of our knowledge, there are no other cross sections for vibrational excitation of furfural available in the literature, so the present data are valuable for this important molecule.